January

Garnet has been the birthstone for January since the 15th century, at least. With a Mohs hardness of 6.5 to 7.5, it can be faceted into beautiful gemstones that wear well in jewelry. Since the term “garnet” actually refers to a group of nesosilicate gems, those born in this month can choose from a rainbow of colors.

The most common members are red almandine, an iron-aluminum silicate; red pyrope, a magnesium aluminum silicate; orange-yellow spessartine, a manganese aluminum silicate; the yellow or green varieties of andradite, a calcium-iron silicate; predominately green grossular, a calcium-aluminum silicate; and rare, bright-green uvarovite, a calcium chromium silicate.

February

From the 15th century to the present, amethyst has been the preferred birthstone for February. Amethyst belongs to a mineral family that can compete with garnet for diversity of color: quartz.

Pure quartz is colorless, as exemplified by Herkimer diamonds. The causes of amethyst’s shades of pale violet to rich purple are radiation and the inclusion of iron impurities and trace elements.

As a rule, amethyst crystals are short and stubby, and occur in large numbers, often filling a large vug a hollow petrified tree section, or lining the inside of a geode. Fine crystals that are large enough to produce a faceted gem of over 20 carats are rare.

March

The current choice of a birthstone for March is aquamarine. Aquamarine is a variety of beryl (Mohs 7.5-8). Its name was derived from the fact that the beautiful, transparent, blue-green coloration of the gem resembles that of seawater. It can be found in translucent to transparent crystals that form in the hexagonal system. The six-sided crystals are often striated lengthwise.

Aquamarine develops in metamorphic rocks and, more often, in pegmatites.

April

Before 1900, a person with an April birthday had two choices of birthstone: diamond or sapphire. During the 20th century, however, diamonds became the preferred stone.

Diamond, a mineral consisting of pure carbon, heads the list of all gemstones for its beauty and hardness. A 10 on the Mohs Scale of Hardness, it is resistant to scratching and is an ideal gem to set in rings. Its hardness results from the arrangement of its atoms in cubes.

All diamonds have slightly rounded faces, and they’re so smooth they feel greasy to the touch. They can be colorless and water clear to blue, pink, yellow, brown, green or black, and transparent or translucent. They shine with an adamantine luster when held to the light.

May

There were two choices for May birthstones for several hundred years: emerald and agate. The popularity of agate seems to have waned at the turn of the 20th century, so emerald is now the favorite. It’s the green member of the beryl family of gemstones. The color varies from bright green to pale green and, sometimes, darker shades of blue-green.

Fine emeralds have a velvety surface appearance and, in the better stones, an even distribution of color. One bad trait of emeralds is a tendency to have inclusions. It’s rare to find an emerald without some slight imperfection. This in no way deters from the beauty of this gemstone, though. It can also be one way of determining whether an emerald is a simulated gem or the real thing, as manmade stones have no imperfections.

June

The contemporary choices for June are pearl, moonstone and alexandrite. Of course, a pearl is the organic product of marine bivalves and not a mineral.

Moonstone is a variety of feldspar that shows adularescence, or schiller, an optical effect that produces a milky luster with a bluish tinge that appears to move across the stone when it is tilted. The phenomenon is named after the feldspar variety adularia.

Alexandrite is a color-change variety of chrysoberyl (beryllium aluminum oxide). This is a very rare and expensive gemstone. It has a hardness of 8.5, and its crystals are either tabular or prismatic. The distinction between alexandrite and chrysoberyl is simply color. A strange characteristic of alexandrite is that it is red, purple or violet when held under artificial light, but in daylight, it looks green.

July

Ruby is the standard birthstone for the month of July. It is a corundum (aluminum oxide) gem that gets its color from the presence of chromium in its structure. An exceptionally hard mineral, corundum illustrates a hardness of nine on the Mohs scale. “Pigeon-blood” red is the preferred color for rubies, though they also occur in lighter shades, including pink. All other colors of corundum are called sapphires.

Ruby exhibits all the desirable properties of a jewelry stone: beauty, durability, optical properties, and rarity. Some rubies display a star or asterism when fashioned into a cabochon. This effect is caused by the reflection of light from numerous inclusions of minute, needle-like crystals of rutile. Corundum crystallizes in the hexagonal system with a tabular-barrel-shaped habit.

August

Current birthstones for August are peridot, the gem-quality form of olivine and spinel. Olivine makes up a large portion of the earth’s mantle. Rocks containing olivine have been brought to the surface by volcanic action and actually blown out in the form of volcanic bombs. Masses of olivine have been found in meteorites, and the Apollo astronauts brought basaltic rocks back from the moon that contained olivine.

A popular jewelry stone, peridot has a hardness of 6.5-7 and can be transparent or translucent, with a vitreous luster. Its color shades from deep green to apple green, yellow-green or olive. It’s most often found in granular nodules, forming short, prismatic crystals in the orthorhombic system.

Spinel is the gem-quality member of the larger spinel group. Its hardness (Mohs 7.5-8.0) makes it ideal for jewelry use. Its spectrum of colors includes red, pink, purple, blue and lavender. In times past, red spinel was often mistaken for ruby. A notable example is the Black Prince’s Ruby, set in the royal crown of England.

September

The birthstone for September is sapphire. This term refers to any corundum (aluminum oxide) gem that has any color other than red (ruby). Sapphires may be colorless, blue, green, yellow, orange, brown, pink, purple, gray, black, or multicolor. At Mohs 9, its hardness is second only to that of a diamond.

Heat treatment is sometimes used to give natural blue sapphires a deeper, more pleasing color. Natural star sapphires, which display the optical phenomenon of asterism, are very rare.

October

Two options for October are opal and tourmaline. Opal is a magnificent gemstone with a play of color or “fire” in all colors of the spectrum. Spaces between the tiny spherules of silica that make up the gem diffract light into its spectral colors. Red, yellow, green and blue, in strong to pastel shades, flash from the stone when it is tilted.

Opal occurs in common and precious types. Common opal does not display any reflective fire. It may have a honey-yellow, brown, gray or colorless body color that is milky and opaque. Opal (Mohs 5-6) is not a very hard gemstone.

Tourmaline, a silicate of boron, has a complicated chemical composition, in which a number of elements, including calcium, iron, sodium and aluminum, may combine. It has a Mohs hardness of 7-7.5.

It belongs to the trigonal crystal system and its habit is hemimorphic (a crystal having two ends of an axes unlike in its planes).

Because of the coloration of the individual stones, tourmaline has several names, including schorl (black), rubellite (red), indicolite (blue), and dravite (brown). Tricolor crystals are common. The popular watermelon variety has an outer layer of green around a red core.

November

The current birthstones for November are topaz and citrine. People tend to think of topaz, a silicate mineral with aluminum and fluorine, as a yellow stone, but heat-treating and color-enhancing adaptations have made blue the predominant color on the market. It is an allochromatic mineral, which means its color is caused by internal defects in the crystal and has a Mohs hardness of eight.

Citrine is the golden member of the quartz family (silicon dioxide). Though quartz in its many forms is one of the most abundant minerals on earth, fine, gem-grade crystals are not that common. Citrine is affordable and, when faceted, rivals more expensive gemstones in beauty.

December

There are three birthstones for December: turquoise, blue zircon and tanzanite. Turquoise (hydrated copper aluminum phosphate) is an opaque, blue-to-green, massive gem material. It has a relatively low hardness of Mohs 5-6, so care must be taken with turquoise jewelry.

The rarest and most valuable variety is robin’s-egg blue with black “spiderweb” veins of limonite. Fake turquoise, consisting of dyed howlite or magnesite, is common. Buyer beware.

Zircon (zirconium silicate) can be blue, black, red, brown, green, yellow, smoky, or water-clear. It has an adamantine luster much like that of a diamond, and it is often misidentified as such.

Tanzanite, the blue/purple variety of zoisite (basic calcium aluminum silicate), is a recently introduced alternative for December. Tanzanite crystals in shades of yellow to brown, green, pink, gray or blue are often heat-treated to produce a gemstone that is a beautiful and permanent blue.

This story about what are birthstones by month previously appeared in Rock & Gem magazine. Click here to subscribe! Story by Kenneth H. Rohn.

The post What are the Birthstones by Month? first appeared on Rock & Gem Magazine.

This iconic World Heritage Site encapsulates a central theme of “Paradise” with its harmonious blending of so many elements including the phrase “Enter Thou My Paradise” inscribed over one entrance.

The Taj Mahal, which translates as the “Crown of Palaces,” has been called the jewel of Muslim art in India. This “ultimate symbol of love and loss” perched above the Yamuna River in Agra in the state of Uttar Pradesh, began with Mughal emperor Shah Jahan, who reigned from 1628 to 1658.

Keeping a Memory Alive

Although he had many wives, Jahan had one great love, his wife Mumtaz Mahal, who died while giving birth to their fourteenth child in 1631. It is said Jahan’s hair turned gray overnight in his grief. To keep his wife’s memory alive forever, he immediately commissioned a great mausoleum to house her remains. Eventually, it would also serve as the tomb of Jahan himself, forever side-by-side with Mumtaz in what was meant to replicate paradise on earth.

Construction began in 1632, and the famous white marble mausoleum was completed in 1648. It took another five years (until 1653) to complete the entire 42-acre complex, which includes reflecting pools, courtyards, gardens, cloisters, crenelated walls, and associated majestic buildings (including a mosque and a guesthouse) constructed in red sandstone from Delhi. But the 115-foot high dome of the mausoleum stands out as the centerpiece. Its translucent white marble from Makrana quarries in Rajasthan (transported nearly 500 miles via bullock carts and elephants) contrasts with the red sandstone of the surrounding buildings and walls. The color of the marble shifts with the hours of the day : pink in the rising sun, white in strong daylight, golden-hued at sunset and under the moon. Some say this was intentional, to replicate the ever-shifting moods of Mumtaz.

Surprising Materials

A surprise for many is that the Taj Mahal is more brickwork than marble. The white marble forms just a thin veneer. Had it been crafted entirely of marble blocks, the tomb would not have been able to support its own weight.

Under the supervision of Ustad Ahmad Lahauri and a board of court architects, construction involved masons, stonecutters, sculptors, and inlay artisans along with the best calligraphers in the land. In all, more than 20,000 laborers formed a city-within-city surrounding the complex in a project that, in its day, was comparable to the Apollo moon shot of the 1960s. And its cost was similarly exorbitant.

How much would it cost to build the Taj Mahal today? Sources are conflicting. In U.S. dollars, numbers range from as low as $70 million to as high as $1 billion. No matter how you do the math and the exchange rate, that is a lot of rupees!

Symbolic Designs

Because the Islamic faith forbids the use of human faces or imagery in decoration, the surface of the mausoleum relies on symbolism to reflect both natural beauty and divinity. Per one source, it was designed to represent “an earthly replica of one of the houses of Paradise.”

Floral Symbols

Architects chose abstract geometric forms, including herringbone inlays here and there, but especially floral designs. Flowers were considered natural symbols of the divine realm.

The designs include realistic vases, flowers, and vines carved in three-dimensional relief and polished within the marble on some panels. Such carved relief works particularly grace the lower portions of the walls.

What really catches the eye are the inlays of stylized flowers. While commonly called peitra dura (“hard stone”) from Italian traditions, in India it is called parchin kari. Precious and semi-precious stones ranging from large slabs to tiny slivers were cut, shaped, polished, inlaid, and leveled to the enclosing marble. The floral patterns they represent include tulips, lilies, irises, poppies, and narcissus. To create shaded effects, a single flower might have a dozen or more carnelian pieces in colors of varied intensity.

Taj Mahal Pattern Books

To this day, Indian artisans hold “pattern books” to craft designs originating with the Taj Mahal into marble countertops, tables, and small jewelry boxes. While few of us will ever be in a position to create or purchase a monument on the scale of the Taj Mahal, parchin kari has long been a vibrant cottage industry in this region of India.

But buyer beware! Quality varies considerably, from the finest marble that is highly durable and takes a fine polish to soft, porous marble or even soapstone that may be inlaid with plastics. The real deal is stunning to behold.

While parchin kari in airport gift shops may go for cheap, Shah Jahan spared no expense in sourcing stones for inlay from all around India, the Middle East, and Asia to grace the mausoleum for his beloved Mumtaz. For instance, carnelian came from Arabia, jade from China, jasper from Punjab, turquoise from Tibet, lapis lazuli from Afghanistan, and sapphires from Sri Lanka. In all, some 28 types of gemstones were used as inlay.

Common Gems in the Taj Mahal

It’s said the lapidary artists decorating the Taj Mahal chose stones “whose luster and color never fades.” Here are just a few:

• White, yellow, and black marble
• Blue lapis lazuli
• Red and orange carnelian
• Green jade
• Blue turquoise
• Jasper in varied colors
• Green malachite
• Green-and-red bloodstone
• Multi-colored banded agates and chalcedonies
• Garnet
• Sapphire

In addition to flowers, inlaid calligraphy composed of jasper and black marble graces several parts of the Taj Mahal, particularly recessed arches. The calligraphy highlights passages from the Qur’an that were chosen by the Persian Abdul Haq, who was greatly admired for his skill as a calligrapher. He used an elegant cursive style known as “thuluth script.” Shah Jahan graced him with the title “Amanat Khan Shirazi” for his work. Such was the attention to detail that calligraphy in higher parts of the building is slightly larger to reduce “skewing effects” when viewed from the ground. Everything about the Taj Mahal had to be pleasing to the eye with balance, symmetry, and harmony.

Taj Mahal Through the Years

Shah Jahan was a rich man with a rich kingdom and as such could afford inlay using the best of precious and semi-precious stones. However, if you were a ruler in a province lacking in resources but you at least wanted to look rich, you had plaster painted to look like inlaid marble or plaster inlaid with colored glass and mirrors simulating gemstones and silver. But, try as they may, none came close to replicating the real deal at the Taj Mahal.

Decorative elements in the Taj also once included gold and silver, including a gold spire atop the main dome. But Agra was invaded in the 18th century by armies of the Jat rulers of Bharatpur. They took away all gold and silver elements, as well as an agate chandelier. At some sites, all precious stones had been pried from walls and it is said that invading armies would pile wood in halls and set it ablaze to capture silver as it melted and dripped to the floors. In light of such carnage elsewhere, we are lucky the Taj Mahal escaped further vandalism over the many centuries.

By the end of the 19th century, the Taj Mahal complex had fallen into a state of disrepair. Recognizing the significance and beauty of even a tarnished Taj Mahal after India had been colonized by the British, viceroy Lord Curzon embarked on a restoration project that was completed in 1908. Despite ups and downs, India and the world continue to recognize and appreciate the beauty, symmetry, and significance of this incomparable gem of love, loss, and paradise. In the words of the poet Rabindranath Tagore, it will forever stand as “a teardrop on the face of eternity.”

Explore More

• Official website of the Taj Mahal: www. tajmahal.gov.in/

• UNESCO Taj Mahal profile: whc.unesco.org/en/list/252

• Explore the Taj Mahal: www.taj-mahal.net/newtaj/textMM/Inlay.html

This story about Taj Mahal gems previously appeared in Rock & Gem magazine. Click here to subscribe. Story and Photos by Jim Brace-Thompson.

The post Exploring Taj Mahal Gemstones first appeared on Rock & Gem Magazine.

Of the three major rock types in the earth’s crust, garnet is most often formed during metamorphism. It is found in schist, especially mica schist, gneiss, and other metamorphic rock. It is found much less often in igneous rocks like granite and even in some pegmatite deposits under the right conditions. Because of garnet’s ranking on the Mohs Scale of Hardness, it survives weathering and so is also found in sedimentary environments.

Almandine Garnet

Near the mouth of the Stikine River, close by Wrangell, Alaska, is Garnet Ledge, one of the better-known almandine garnet deposits. Specimens from here have been collected for over a century starting with gold prospectors. This area was once owned by the Boy Scouts and Juneau’s Presbyterian Church. It is now a registered Wilderness area held in trust for the children of Alaska.

Today, you can see the simple 12-sided almandine crystals in mica schist from the Ledge worldwide in museums, in private collections, and to a lesser degree, in jewelry. These crystals are choice examples of an iron aluminum silicate garnet. They are not well known for their gem quality.

Alaskan almandine garnets are considered special in the business world. In the early 20th century, the deposit was owned and operated by the Alaska Garnet Mining and Manufacturing Company. This was the first-ever business corporation in America fully owned and operated by women.

Almandine garnets are easy to recognize because the mineral usually forms in 12-sided crystals that are very hard. They are 6.5-7.5 on the Mohs scale. They survive after the host rock has been weathered away.

For decades, the most common garnet available was almandine; this is because it was heavily mined for its abrasive qualities. You can buy garnet paper in any hardware store, and it is most often crushed almandine.

Types of Garnets

Garnets occur in a wide variety of localities and types but are most common in metamorphic rock types. Mineralogists list no fewer than 16 different members of the garnet family, all silicates.

Of these, six varieties are prevalent. They are almandine, pyrope, spessartine, uvarovite, grossular, and andradite. They are listed as two sub-groups, pyralspite and ugrandite, based on their chemistry and using portions of their mineral names.

The pyralspites are pyrope, almandine, and spessartine, and all have aluminum as the main metal. Either iron joins the aluminum to form almandine, magnesium to form pyrope, or manganese to form spessartine. The atoms of those three elements can interchange because of their similar size and electron structure. This forms a series that grades one into the other.

The ugrandite group has three garnets: uvarovite, grossular, and andradite, all have calcium as the main metal. Iron-forming andradite joins the calcium or chromium to form uvarovite. Aluminum joins the calcium to form grossular garnets.

Garnet Formation

Garnets formed in metamorphic rocks can tell scientists the approximate pressures and temperatures that particular rock was subjected to during metamorphic action.

As the garnet is forming under high pressures and temperature, its crystallization, lattice structure, and internal crystal zoning are affected. This tells scientists about the forces involved in metamorphic action. Garnets may also tell scientists how long ago the rock formed through any trace of lead-uranium it may contain.

Roxbury Garnets

Roxbury garnets are the Connecticut state mineral. Connecticut is done of several states that have chosen garnet as the state gem, including New York and Idaho. The State Gem program was established by the American Federation of Mineralogical Societies.

By comparison, the almandine garnet deposits in upper New York State at Gore Mountain eclipse the size and quality of the Connecticut deposit. The New York garnets are often gemmy and can be used in jewelry.

As for size, the Roxbury crystals tend to be an inch or so in size, while the Gore Mountain crystals often measure several inches across in crystalline masses.

Discovery of Tsavorite

Geologist Campbell Bridges discovered a deposit of green grossular garnets in 1967 in the Merelani Hills, Tanzania, already known for tanzanite. The grossulars were gemmy and a rich green that rivals emeralds.

Campbell’s further searches found similar geologic formations that extended into Kenya. There he found another deposit rich in grossular garnets as gemmy and bright as the original find.

Working with Tiffany & Co., Campbell mined the garnets and, between them, the companies named the grossular gems tsavorite after the Tsavo National Park near the Kenya deposit.

Grossular garnets are calcium aluminum silicate. The calcium atoms can be replaced by other elements, which means grossular can be a range of colors: green, pink, gray, brown, even black. Tsavorite is unique because the rich green color is caused by either vanadium or chromium in its chemistry.

Spessartine Garnets

Another recent exciting garnet find is that of spessartine garnets, named for Spessart, Bavaria, where they were first found in quantity.

Chemically, spessartine garnet is magnesium aluminum silicate and can be found in several different colors: yellow, red and violet-red.

Under the right light, some crystals will show a change of color. Most form in metamorphic rock and skarms, but a recent amazing discovery was made of red spessartine crystals on aquamarine crystals in a gem pegmatite in Pakistan.

The garnet family of crystals is one of the mainstays of mineralogy and our hobby. Every collector, even the most inexperienced, can field collect them and learn from them. Even the most advanced collector can also own and enjoy a suite of rare garnet crystals. Garnets are truly worthy of being in every collection.

This story about what are garnets previously appeared in Rock & Gem magazine. Click here to subscribe! Story by Bob Jones.

The post What are Garnets? first appeared on Rock & Gem Magazine.

Abrasive Appeal

The word “garnet” refers to a group of complex silicate minerals with similar crystalline structures but diverse chemical compositions. Garnet’s general chemical formula is A3B2(SiO4)3, with “A” representing such divalent metallic ions as calcium, magnesium, ferrous iron, and manganese, and “B” representing trivalent ions like aluminum, chromium, ferric iron, and manganese. In certain rare garnets, the “B” cation can also include vanadium, titanium, or zirconium ions. 

Many of the 14 garnet-group members form mutual solid-solution series. The most familiar and abundant of these garnet minerals are almandine, pyrope, spessartine, grossular, andradite and uvarovite. Garnet-group members vary widely in color, but only slightly in hardness, density, and index of refraction. 

Garnet crystallizes in the cubic system, usually as dodecahedrons and trapezohedrons. Garnet’s Mohs hardness of 7.0-7.3 makes it somewhat harder than quartz (Mohs 7.0). With specific gravities ranging from 3.56-4.32, garnet is considerably denser than quartz (specific gravity 2.65). 

Quartz sand has traditionally been the most widely used industrial abrasive because of its very low cost. But garnet, which offers many advantages that override its higher cost, is now displacing quartz sand in many abrasive applications.

Differences in Mineral Behavior

Under the severe stresses of abrasive use, garnet and quartz behave quite differently. Both have a conchoidal fracture and no cleavage, but quartz’s tetrahedral atomic structure makes it the tougher and more durable mineral. Quartz breaks into rounded grains of the type found in the world’s dune fields and beaches. Garnet grains, however, do not become rounded; they break into sharp-edged bits that retain their abrading efficiency.

Quartz sandblasting agents can be used but once and cannot be recovered. But garnet mediums, with their significantly greater density, are easily recovered by inexpensive, hydraulic separation or “washing” methods. And because garnet grains retain their sharpness, they can be reused many times.

Garnet also has important health-related advantages. Quartz sandblasting agents create airborne dust of fine silica particles which, when inhaled, form silicic acid. Over time, silicic acid literally petrifies delicate lung tissues and greatly impairs pulmonary function. This debilitating industrial disease, called silicosis, can be fatal. Although garnet sandblasting agents also create airborne dust, it is non-toxic. 

Garnet Applied Benefits

So while quartz-sand abrasive mediums cost less initially, garnet is cheaper in the long run for growing numbers of industrial applications.      

The petroleum industry uses huge amounts of garnet sandblasting agents to clean compacted mud and silt from drill pipes and well casings. Garnet powder and grit is also used to polish optical lenses and metal, and as a media in filtration systems for water and industrial liquids. A rapidly growing use is as the abrasive agent in water-jet cutting, which eliminates the need for flame cutting in many manufacturing operations.    

While quartz sand remains the leading industrial abrasive, demand for industrial-grade garnet continues to increase.  Although garnet is relatively abundant with many occurrences, it has few major mine sources. Most garnet is mined from alluvial or beach deposits. China and India each account for one-third of world production. Australia is third at 15 percent. 

The United States consumes 17 percent of world garnet production, but mines only three percent. In 2017, domestic garnet production amounted to 38,000 tons of refined garnet concentrate worth $11 million.

While garnet gemstones are also mined commercially, their quantity and value are minuscule compared with those of industrial-grade garnet.

This story about garnet industrial uses appeared in Rock & Gem magazine. Click here to subscribe. Story by Steve Voynick.

The post Garnet’s Industrial Uses first appeared on Rock & Gem Magazine.

Gold panning, the simplest form of hydraulic gravitational separation, relies on differences in mineral density, which is measured in specific gravity. The specific gravity of quartz, the primary component of most sands and many rocks, is 2.65. That of native gold is most often between 17.0 and 18.0. Because of gold’s far greater density, it remains in the pan while the common, quartz-based gravels are washed away.

Most Common Concentrates

Most gold-pan concentrates consist of relatively dense, iron-based minerals such as magnetite (iron oxide, ferrous-ferric), hematite (iron oxide, ferric), ilmenite (iron titanium oxide), and chromite (iron chromium oxide), all of which have substantial specific gravities. between 4.3 and 5.3. Their generally dark colors are the origin of the term “black sand.”

With careful panning techniques, minerals with specific gravities as low as 2.9 will remain in the pan concentrate.

These minerals can include everything from the sulfides, oxides, and carbonates of heavier metals to such relatively dense gemstones as diamond, ruby and sapphire (corundum), topaz, garnet, spinel, and chrysoberyl.

Concentrates Aid In Deposit Discovery

Both the historic silver discoveries at Nevada’s Comstock Lode and Leadville, Colorado, were made by gold miners who identified oxidized silver minerals in their pan concentrates. Gold panners also discovered Montana’s five major sapphire deposits.

Sometimes pan concentrates can be a big problem. I once sluiced gold-bearing gravels in an Alaskan creek—where the pan concentrates consisted largely of tiny bits of native lead—from which the gold particles could be separated only by amalgamation.

Even in this age of high-tech mineral exploration, panning remains a valuable prospecting tool for many minerals other than gold. In the late 1980s in northern Canada, pan concentrates led to the discovery of diamond-bearing kimberlite pipes.

Prospecting for ‘Indicator Minerals’ Pays Off

When exploration geologist and prospector Chuck Fipke panned his way across 400 miles of tundra, he was not searching for diamonds per se, but for the “diamond-indicator” minerals that typically associate with diamonds in kimberlite environments, but are much more abundant and readily identifiable.

Fipke was specifically looking for black ilmenite (iron titanium oxide), red pyrope garnet (magnesium aluminum silicate), and green chromium-rich diopside (calcium magnesium silicate), which all have sufficient densities to be retained in pan concentrates.

During several years of prospecting, Fipke never panned a single diamond. He did, however, follow a trail of ilmenite, pyrope, and diopside. He eventually panned a green diopside crystal with no alluvial wear at all—enough to convince him that he was standing atop the eluvial remains of weathered kimberlite pipe. Core drilling revealed a kimberlite pipe that has since been developed into the billion-dollar Ekati diamond mine.

Along with the common black sands, you’ll find an array of other minerals with densities mostly in the 3.0-5.0 specific-gravity range.

Under a loupe, the combination of colors can be eye-catching. The common garnet-group minerals impart bright orange, pink, and red hues. Some concentrates even have a “Christmas tree” appearance when garnets mix with another common, dense mineral—green epidote (basic calcium aluminum iron silicate).

Panning Leads to Fascinating Discoveries

Although many minerals in gold-pan concentrates are abraded and rounded from alluvial wear, some retain enough of their original crystal forms to aid in identification.

So gold pans are not just gold-recovery tools, but geological sampling instruments. Take a closer look at those ubiquitous “black-sand” concentrates and you’ll be pleasantly surprised at the cornucopia of interesting minerals that meet the eye.

This story about gold pan concentrate appeared in Rock & Gem magazine. Click here to subscribe. Story by Steve Voynick.

The post What are Gold-Pan Concentrates? first appeared on Rock & Gem Magazine.

Spessartine is a mineral that often garners a double take for its crystal habit and its incredible color.

Sometimes described as a reddish-orange or even blood red, based on its formation of solid solution series with almandine, the commonly deep richness of the color of this member of the garnet family is on par with its unique story.

The type locality of this mineral, and the area for which it was named, is the Spessart Mountains of Bavaria, Germany. The mountain range crosses the German states of Hesse and Bavaria and is marked by dense forest hills and valleys where ancient beech and oak grow in volume. In addition, the area is known for the presence of red sandstone (known in Germany as buntsandstein), which is said to have formed 250 million years ago.

Discovery Alters Rarity

According to Minerals.net, this manganese aluminum silicate garnet was considered a rare find for quite some time until an exciting discovery in 2008. Far from its type locality of Bavaria, Germany, a deposit near the Serengeti National Park in Tanzania served as the place of discovery for brilliant orange examples of Spessartine crystals.

Before the discovery in 2008, the last significant discovery of spessartine took place in the late 20th century in Tongbei and Yunling, Zhangzhou Prefecture, China. These examples were best known to appear as “gemmy crystals coasting Smoky Quartz,” as reported on Minerals.net.

Other notable localities for spessartine specimens include deposits in historic Minas Gerais, Brazil, which is the locality for the specimen featured in this Mineral of the Week; New South Wales, Australia; and Iveland, Aust-Agder, Norway, among others.

Spessartine has also been discovered, albeit more sparingly, in the United States, in deposits including the Little Three Mine and the Pack Rat Mine, both in San Diego Co., California; Ruby Mountain, Chaffee Co., Colorado; and the Thomas Range in Juab Co., Utah, to name a few.

Perhaps one of the lessons we can take from spessartine is not to consider a mineral to be completely uncommon but, instead, just not yet fully discovered.

The specimen of spessartine featured in this Mineral of the Week was extracted from the Navegadora claim, Conselheiro Pena, Minas Gerais, Brazil. The specimen, which measures 5.1 x 3 x 2.9 cm, is described as having great luster, translucency, and many geometric crystal faces. The specimen is offered by Isaias Casanova through Mineral-Auctions.com.

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The post Mineral of the Week: Spessartine first appeared on Rock & Gem Magazine.

A new year brings many things to the forefront, including the January birthstone: garnet. The striking beauty of this stone is equaled by its centuries-long popularity. As archaeological and literary research reveals, red garnet was among the most common stone of jewelry worn by ancient Egyptian pharaohs and members of royalty, and in ancient Rome, red garnets were highly sought-after in the trade market.

As if that isn’t enough fascinating reasons to showcase garnet, Jim Perkins, the man behind Faceting Focus, reports receiving many requests about a garnet cut pattern he created. Perkins aptly named the pattern, Fire Engine Garnet.

“Red garnets have deep saturation of color,” Perkins states. “They show this color when you shine a light through them. However, when they are cut, they often look extremely dark, almost black. Making them mysterious and difficult to cut.”

Revealing Lush Color Through Cut

Perkins worked with a piece of rough Rose Almandine Garnet, provided by New Era Gems (www.neweragems.com) in creating this pattern. To help reveal the bright and lush color of the garnet, he created a well-proportioned stone that isn’t extremely deep.

“I have learned to make designs that are fun and easy for others to reproduce,” Perkins states. “I enjoy sharing my designs with others to cut.”

With the holidays underway, gift-giving is top of mind for many, and well before this time of the year, it’s something Perkins thinks about.

“My inspiration for faceting and designing have always been my family and friends,” he says. “I love to give gifts, and I could never afford to give a better gift than one that I made.

“Anyone can buy gifts, but if you take the time to create something new and different, then make it. The gift is priceless.”

Exploring New Stones and New Ventures

Just as many of us take time to look back on the year that was and look forward to a new year and consider goals we’d like to work towards, Perkins shares a couple of exciting instances of 2019 and something he’s looking forward to in 2020.

“Steve Ulatowski of New Era Gems has introduced a new color of blue topaz to the market. It is called Tahoe Blue Topaz,” says Perkins, who has already purchased a piece. “I have created a new PEAR design to cut it, and I am looking forward to finishing that project in 2020. I think it will be stunning.”

In addition, Perkins, who has authored numerous books, has just finished a new faceting design reference, “Adventures in Faceting.”

Whatever goals and projects are on the horizon for you in 2020, as Perkins demonstrates in his work and commentary, draw on what inspires you most and always keep learning.

Faceting Focus is sponsored by

The post Faceting Focus: Reveling in Fire Engine Garnet first appeared on Rock & Gem Magazine.

Gem-and-mineral shows are fascinating for their huge displays of mineral specimens, gemstones, gems, carvings, jewelry items, and trinkets. But visitors sometimes overlook the most abundant items of all—beads. Manufactured by the billions, eminently affordable, and part of our everyday lives, beads are easy to take for granted.

Beads are defined as “small bits of material perforated for stringing and worn as ornamentation.” But the utter simplicity of this definition belies their fascinating history.

Early Adornments

As the first durable ornaments that humans ever possessed, beads are among the most abundant of all archaeological recoveries. Over many millennia, beads have played enormous roles in history and commerce, while their manufacturing methods, past and present, have reflected the progress of technology. As part of the art, culture, religions, and jewelry of every post-Paleolithic society, beads are truly a mirror of humanity.

Available in every imaginable color, color combination, degree of transparency, size, shape, and texture, beads have been fashioned from virtually every durable material—natural and synthetic, metal and nonmetal, organic and inorganic. And beadworking—the art of arranging many individual beads into complex patterns—continues to invite artistic creativity in cultures worldwide.

The first beads, made during the late Paleolithic Period more than 100,000 years ago, were fingernail-sized marine shells, perforated, often stained red with powdered hematite, and showing abrasion marks from wearing or carrying on strings. They represent the earliest anthropological evidence of the emergence of sophisticated, symbolic-material cultures capable of abstract thought and of appreciating the value of non-functional objects.

Beads Become Talismans

With only crudely pointed stone tools as “drills,” Paleolithic bead-makers’ materials were limited to thin, flat disks of shells and organic matter, along with soapstone (talc, basic magnesium silicate) and other very soft stones. Beads gained widespread popularity about 30,000 BCE when European hunters began stalking migrating herds of mammoths, bison, and caribou. With successful hunting vital to survival, these Ice Age hunters wore beads as talismans—charms that would hopefully avert evil and bring good fortune. They believed that beads made from their quarry’s teeth, ivory, horn, or bone would impart to themselves some of their quarry’s speed, strength, and cunning.

Archeological evidence indicates that beads were initially worn singularly.

Multiple stringing became common only after 28,000 BCE reflecting, as anthropologists suggest, an emerging human conviction that if one bead was good, more beads were better.

Nomadic humans established their first rudimentary communities about 20,000 years ago. With closer communal contact, beads began serving both as objects of personal adornment and as symbols of identity and rank.

Drilling remained a major impediment to bead-making until 16000 BCE, when beads’ growing societal importance spurred several major technological advancements. Bead-makers began drilling longer, needle-like holes in stone with bow drills that rapidly rotated quills or thin bird bones filled with a powdered-quartz paste. The realization that the abrasive paste, rather than the drill itself, actually performed the drilling was a quantum leap forward in both mechanical comprehension and the art of bead-making.

Bead-makers next learned the technique of double-drilling—drilling halfway through a stone from opposite sides until the holes met in the middle. The combination of bow drills, abrasive pastes, and double-drilling opened the mineral world to bead-makers. No longer restricted to organic materials and soft rocks and minerals, they began utilizing the hard, colorful agate, jasper, and carnelian varieties of microcrystalline quartz. They were also able to manufacture beads with more-difficult-to-drill spherical and ovoidal shapes.

The Neolithic, the last Stone Age period, began about 10,000 BCE when climatic and environmental changes triggered major cultural transitions. As climates warmed and continental glaciers retreated, many hunters became gatherers. The Neolithic revolution began about 5000 BCE when certain plants and animals were domesticated in Europe and western Asia. The first modern civilizations appeared as nomadic gatherers became settled food producers. With the subsequent specialization of labor, full-time bead-makers dramatically increased bead production.

New Age Brings New Bead Materials

As the Neolithic Period melded into the Copper and Bronze ages, the most prized bead-making materials were lapis lazuli, jade, amber, turquoise, carnelian, and garnet.

Lapis lazuli is a metamorphic rock in which the mineral lazurite, a complex sodium calcium sulfosilicate, imparts a deep-blue color. Mining began about 6000 BCE at Sar-i-Sang (Sar-e-Sang) in Badakhshan, Afghanistan, making lapis lazuli the first gemstone ever to be systematically mined. Lapis lazuli beads were a major trading commodity throughout antiquity, and Afghanistan remains the leading source of the gemstone today.

Carnelian, the translucent, red-to-orange variety of microcrystalline quartz, was being fashioned into beads in Europe, the Middle East, and India by 5000 BCE. Obtained mainly from India and Turkey, carnelian was valued for its warm colors. Early bead-makers also worked with other quartz gemstones, including opaque jasper, multicolored agate, golden citrine, purple amethyst, and colorless rock crystal.

By 3500 BCE, Egyptians in the Sinai Peninsula were systematically mining turquoise, a basic calcium aluminum phosphate. With their bright, blue-to-blue-green colors, turquoise beads were in great demand throughout the entire Mediterranean region. Bead-makers also utilized several other oxidized copper minerals that often occur in association with turquoise, most notably forest-green malachite.

Ancient China’s most prized bead-making material was the nephrite form of jade, a calcium magnesium silicate, which was mined before 5000 BCE. Of nephrite’s many colors, green was most highly valued. Known as yu or the “royal gem,” green nephrite was thought to ward off evil and injury. The large-scale manufacture of jade beads began in China about 3500 BCE.

Garnets Lead the Way For Faceted Beads

By 3100 BCE, Egyptian bead-makers were working with red garnet, mostly pyrope (magnesium aluminum silicate) and almandine (iron aluminum silicate). The availability of garnet influenced several aspects of bead-making. The first “faceted” beads were garnet crystals with smooth, natural dodecahedral crystal faces. The concept of faceting gemstones into gems may have originated with the highly reflective, natural crystal faces of garnet beads.

At Mohs 7.5, garnet is substantially harder than quartz (Mohs 7.0). In powdered

form, it is an ideal abrasive for drilling and polishing other bead materials, especially quartz.

Another early bead material was amber, a fossilized (polymerized) tree sap found in quantity on northern Europe’s Baltic coast. Amber offered bead-makers warm, pleasing colors, a glowing translucency or semi-transparency, and a softness (Mohs 2.0-2.5) that greatly facilitated drilling.

Amber was the first gem-like material used for personal adornment. Amber beads have been found in late Paleolithic burial sites dating to 15000 BCE. After 3000 BCE, beads of Baltic amber were traded throughout Europe and the Middle East.

The first metal beads, made of native copper hammered to flatness and drilled, were found in burial sites in northern Iraq dating to 8000 BCE. The earliest tubular beads were made of tiny, rolled copper sheets.

Precious Metals Beads Garner Attention

The earliest-known gold beads were made in eastern Europe about 4600 BCE. By the dawn of the Bronze Age, roughly 3000 BCE in Europe and the Middle East, copper and gold beads were already common and were soon followed by those of silver, tin, lead and, later, the copper-tin alloy bronze.

Bead-making flourished in the advanced civilizations of Egypt, India, and Mesopotamia. While beads served for personal ornamentation within these societies, most were actually traded to less advanced cultures and tribes, establishing an economic pattern that would influence history for millennia to come.

The first synthetic bead-making material was faience, a siliceous ceramic material that appeared simultaneously in Mesopotamia and Egypt about 3000 BCE. A forerunner of glass, faience was prepared by mixing silica (crushed quartz sand) with natron, a basic sodium carbonate and a common evaporite mineral in desert areas. The natron reduced the melting point of the silica and firing produced a ceramic material with a glassy luster.

After molten faience had solidified in tubular molds, the casts were cut into individual beads and drilled. Molten faience coatings could also “upgrade” beads of soapstone and other soft, easily drilled materials. Faience-coated, inexpensive soapstone beads became the first costume jewelry, eminently affordable, yet gleaming with the same vitreous luster of costly gemstone beads.

The first widely popular bead design featured “eyes.” Decorated with circular patterns representing human eyes, faience “eye beads” supposedly offered protection from the “evil eye”—meaning malevolence or unseen danger. Eye beads originated simultaneously in Egypt, the Middle East, and China; their basic design was the first to transcend entire civilizations.

Bead-Making Techniques Evolve

Faience opened new directions for artistic creativity, but bead-makers also continued working with natural materials. By 2500 BCE, Mesopotamia’s bead-makers were artistically “etching” carnelian beads by painting them with a dot, circle, and zig-zag patterns with a powdered-natron paste. When fired, the natron and silica reacted to form a lustrous, snow-white sodium-silicate glass that was permanently bonded to the carnelian surface. Agate, jasper, and other quartz gemstones could also be chemically etched.

About the same time, Egyptian bead-makers originated the art of beadworking—

interweaving strands of differently colored beads into complex patterns to decorate tapestries and garments. In Egyptian beadwork, tiny, drably colored, inexpensive “spacer” beads fixed the artistic arrangements of larger, more valuable decorative beads. Since spacer beads were far too small to drill, bead-makers first drilled oversized beads, then ground them down to smaller “spacer” sizes.

Egyptian bead-makers also began cutting agate, onyx, and other patterned stones to display their natural banding. Cutting, an adaptation of the abrasive drilling process, was performed with tough horsehair cords impregnated with powdered garnet.

By 2000 BCE, Egyptians had formulated true glass by adding lime (calcium oxide) to the faience silica-soda mix. The lime hardened the glass and extended the thermal range in which viscid, molten glass remained workable.

Although the first glass was opaque with drab, gray-green colors, Egyptian glassmakers learned to add chromophores of powdered cobalt and copper minerals to create opaque glass with saturated blue and blue-green colors that closely imitated such costly gemstones as lapis lazuli and turquoise.

Cultures Share Techniques

Egyptian bead-makers then developed the technique of “core-winding”—twisting strands of molten glass around thin ceramic cores to form tiny tubes. When the glass solidified, they cut the tubes into individual beads, each with an easily removable ceramic core that negated the need for laborious drilling. By 1500 BCE, core-winding and the availability of true glass had made Egypt’s Middle Kingdom the first of three great periods of ancient bead-making.

Other Mediterranean cultures adopted Egyptian bead-making techniques. By 700 BCE, the Phoenicians artistically applied colored molten glass to core-wound beads to create “head beads.” Shaped like miniaturized human heads, head beads had three-dimensional faces and details as fine as the pupils of the eyes.

The second great ancient bead-making period flourished in Rome, where glassmakers produced the first colorless, transparent glass that was easily colored with chromophores: iron oxides for black, brown, and green; copper oxides for green, blue, and ruby-red; antimony oxide for yellow; and manganese dioxide for a purple glass that imitated natural amethyst.

Rome’s greatest contribution to bead-making was developing millefiori (“thousand flowers”) beads. Roman bead-makers arranged thousands of delicately drawn, needle-thin, colored-glass rods in parallel bunches to form multicolored, cross-sectional patterns or images of human faces, animals, and flowers. After heating to a semi-molten state, they drew the bunches into long, one-quarter-inch-diameter strands.

The miniaturized, cross-sectional color patterns remained intact with remarkable preservation of detail. A tiny portrait of a woman even showed the individual beads in her necklace. Bead-makers cut the patterned cross-sections into thin disks and applied them to the semi-molten surfaces of other beads to produce colorful millefiori beads, each with a dozen or more, detailed miniature images.

Prolific Production of Glass Beads in Ancient Rome

The Romans traded millefiori beads to regions as distant as Scandinavia, India, and equatorial Africa. Historians estimate that Rome manufactured more glass during the first century CE than had been made in the previous 1,500 years, with most used in bead-making.

Rome’s sprawling empire provided many natural bead-making materials: jet

from England, amber from the Baltic region, and coral and pearls from the Persian Gulf. Egypt supplied hexagonal crystals of amethyst and emerald which, when cut cross section and drilled, were among Rome’s most valued beads.

Following the fall of Rome, the Byzantine Empire hosted the last great ancient bead-making period. Although the Koran’s encouragement of modesty in personal dress limited the domestic bead market, Constantinople’s bead-makers improved upon Roman technology to manufacture tons of high-quality beads for the African trade.

During the Dark Ages, the most noteworthy bead-making innovation in Europe and the Byzantine Empire was the development of the cloisonné style. By emphasizing enamel and inlaid gold on red garnet, bead-makers imitated in miniature the colorful stained-glass windows of cathedrals and mosques.

By 900 CE, the Vikings of northern Europe had developed a bead jewelry that emphasized carnelian, rock crystal, and amber. They also traded for Mediterranean glass beads which they combined with beads of natural materials to create elaborate necklaces. The Vikings were also first to introduce European beads to North America.

Multiple Uses for Beads

Prayer beads, which served as numerical aids in prayer rituals and religious incantations, had originated with Hindus and Buddhists about 500 BCE. During medieval times, they reappeared among Europe’s Christians as “rosary” beads. These were often made of jet, black coral, obsidian, exotic hardwoods such as ebony, and amethyst, the latter the gem of bishops’ rings and a Christian symbol of piety and celibacy.

The English word “bead” actually stems from the Middle English bede, meaning “prayer bead,” and the Old English biddan, “to pray,” alluding to the use of beads as “prayer-counters.”

“Worry” beads, which had originated in Turkey and Greece about 500 BCE, also gained popularity in medieval Europe. Worry-bead strings initially consisted of 33 smooth, relatively large, spherical beads, the comforting tactile sensation of which seemed to dispel anxiety. As a secular alternative to rosary beads, worry beads provided comfort without publicly indicting allegiance to any religious doctrine. Worry beads were often made of amber because of its comforting warmth to the touch.

By 1400 CE, Europe was poised to embark upon its great renaissance of science and art, and an unprecedented era of exploration, discovery, and colonial exploitation. The European ships that sailed for Africa, the Far East, and the Americas would all carry sacks and chests of beads as trading commodities, and many would return carrying the beads of distant cultures.

Although already ancient, beads were really just coming of age. With new manufacturing techniques, materials, and markets, they would soon exert their greatest impact ever on the world’s economies and cultures.

The post The Ancient World of Beads (Part I) first appeared on Rock & Gem Magazine.

A round brilliant is often the first cut a new faceter learns. After that first cut, most become anxious to learn how to cut a “fancy shape.”

Fancy shapes are anything besides a round stone. I spent a lot of time developing computer-generated oval designs and other fancy shaped designs that are easy enough for beginners and also an enjoyable experience for advanced faceters. I avoid pre-Gem Cad designs, due to inaccuracies I’ve discovered. I would rather create my own designs using Gem Cad for Windows®.

For this project, I have designed a 10 X 8 millimeter oval with a brilliant pavilion and brilliant-cut crown.

To test cut the design, I have chosen a Swiss lab-grown Padparasha Sapphire, as it is a beautiful color and inexpensive. The design will work in garnet, corundum, and zircon with no changes.

WHAT YOU NEED FOR THIS PROJECT

To cut my oval, I used a FACETRON faceting machine, a 260 diamond top plate for rough cutting, a 600 diamond top plate for fine grinding, and a 1200 diamond top plate for extra fine grinding. I used a BATT LAP with 3,000 diamond powder and candle oil for lubrication for pre-polishing, and a BATT LAP with 100,000 diamond powder and candle oil. All laps are supported on a MASTER LAP. I set the rough on a flat dop using Raytech Diamond Dop, which keeps it from heating up too much and coming off the dop. I also transfer the stone to a cone dop using 5-minute epoxy, and it cures overnight. After the transfer is complete, I put the cone dop in the dop chuck and align the girdle on the master lap. This ensures I will cut a straight crown girdle line.

GETTING STARTED

The first step is to study the faceting diagram and understand it thoroughly. Then cut the P1, P2, P3 & P4 facets to a temporary center point using the rough cutting lap. Then cut the P5 facets near to finished sized.

I cut mine so when I measure across the junction of the facets my digital caliper reads ~ 9 millimeters.

I proceed to cut the P6, P7, and P8 facets so they meet at the junction of their respective pavilion facets to make a straight pavilion girdle line. P6 will meet at the P2’s, while P7 will meet at the p3’s, and the P8’s will meet at the P3’s, as shown in the diagram.

Now go to the 600 lap and cut the size down by ~ .5 millimeters. Using the 1200 lap, cut it down to just a bit larger than 8 millimeters wide. Then proceed to the 3,000 BATT LAP and pre-polish at 89°. You only need to polish the portion of the girdle that will be kept. In my work, I don’t polish any further for the girdle.

Now return to the pavilion and cut using the 600 and 1200 laps. Then pre-polish using the 3,000 BATT LAP and the 100,000 BATT LAP. Be careful not to cross-contaminate the 100,000 lap. Lastly, you can use the 3,000 BATT LAP to cut the pavilion mains. Or if you’d prefer, go back to the 1200 lap to cut, and then polish using the BATT LAP and 100,000 diamond. When you are finished you can transfer your stone into a cone dop with 5-minute epoxy.

FACETING THE CROWN

Once I have the P5 girdle facets adjusted so they are parallel to my master lap, I cut and then inspect to make sure the crown girdle line is level and straight. If not, I make further adjustments to the alignment. If it is level, you are ready to proceed. It’s a good idea to wear an Opti-Visor so you can see the girdle line better. I start my crown with a 600 diamond lap followed by a 1200 diamond lap. Make sure to leave the girdle a bit thick as you continue working the stone, that way you will have enough thickness to work it down.

I cut the meet points precisely using my BATT LAP 3,000 diamond and oil. I recommend cutting slowly and taking breaks to rest your neck and back. Upon resuming, I use my 1200 diamond lap to cut the table, followed by using a plastic Dyna-Lap and 100,000 diamond on my master lap.

Once you complete the crown and table you can heat the cone dop and release the stone from the epoxy. Let it cool and then soak overnight in a sealed jar with Acetone.

SOME CUTTING TIPS

When you cut “fancy shapes” it can be difficult to achieve the exact nominal size. I believe if I cut my stone and the finished size is + .000, -.5 millimeters, that is good enough because settings with prongs have enough adjustment to compensate. In fact, if the stone is slightly undersized I find it easier to set than if it is oversized. I cut the table in to meet points after I have cut the crown breaks, mains, and stars. You’ll want to make sure the top points of all of the mains are touching the table. Sometimes you have to over cut some mains to touch others. If this happens, don’t worry about it.

After the table is polished, place the dop back into the dop chuck and polish the crown in the same order you cut. When you get to the stars that are on either side of an overcut main, cheat the angles of the stars upwards. To do this, lower the angle and raise the mast height. Depending on how much you need to cheat, you may have to lower the facet angle of inclination a few tenths of a degree to as much as one degree. Remember, you will use the same angle on the stars flanking the main. You may be lost doing this in the beginning, but after a while, you will become skillful.

With the FACETRON I rarely use the left and right cheater dial. However, vertical cheating is very common, especially on fancy cuts. When you feel the heat in your stone from friction during polishing, take a break and let the stone cool down. Otherwise, it may move on the dop or come off the dop completely. Another helpful reminder is to always use plenty of oil on your BATT LAP to keep the stone well lubricated and cool.

CONCLUSION

If you are thinking that this stone was a lot more work than a round brilliant. You’re right, it was. This is why fancy cut gems cost a lot more than round brilliants. They are labor-intensive.

In a future design, I will feature an oval design with a keel pavilion that will work for various materials, from quartz to higher refractive indices. It will take a while to cut, but it will make a spectacular gem. Remember that it is not important how fast you cut gems, but much more important to take your time, enjoy the experience and do the best job you can.

The post Faceting Focus: Cutting a Brilliant Oval first appeared on Rock & Gem Magazine.

The Organ Mountains are one of the most stunning ranges in New Mexico. Anyone driving past Las Cruces on Interstate 10 will have an excellent view of the mountains. The granitic core of the range forms a jagged, sawtooth pattern east of the Rio Grande. Early Spanish explorers thought they resembled the organ pipes of European cathedrals, and the mountains were referred to as Los Organos, or the Organ Mountains.

Like all mountain ranges in New Mexico, the Organ Mountains were painstakingly explored by prospectors searching for gold and other metals. Virtually all near-surface deposits of metals were discovered quickly and mined if they had enough ore. The Organ Mountains were no exception, and several former mines lie along the flanks of the mountains.

While the Organ Mountains have several former mines, many are inaccessible for mineral collectors. Much of the eastern side of the Organ Mountains is part of White Sands Missile Range, and it is not possible to access any mines in this area. Private land and fences also block access to many of the mines that are not within the Missile Range. Many of the mines that remain accessible can take considerable effort and time to reach.

Turning to Mine Memoirs for Information

Fortunately, there is an area just north of the Organ Mountains that has some easy-to-reach mine workings with collectible minerals. This is the area of the former Memphis mine, which is just north of U.S. Route 70 and northeast of the town of Organ. The mine lies along the foothills of the San Agustin Mountains, which are just north of the Organ Mountains. The USGS topographic map for the area, which is Organ, New Mexico, indicates there are three shafts in the area of the mine.

One of the best references on the geology of the Memphis mine area is Memoir 36 of the New Mexico Bureau of Geology and Mineral Resources. “This is Geology of the Organ Mountains and Southern San Andres Mountains,” by William Seager, and it was published in 1981. This outstanding guide is available at https://geoinfo.nmt.edu/publications/monographs/memoirs/36/. This download is extremely useful since it also has the geologic maps that go with the report. Many online reports only provide the text and do not have key maps.

The Memphis mine reportedly produced $200,000 to $400,000 worth of copper, zinc, and silver during its operation. The deposits are described in Seager’s paper as replacements of west-dipping strata of Lead Camp Limestone adjacent to the Sugarloaf Peak quartz monzonite porphyry. The Lead Camp beds contain ore at four different horizons, separated by marble or barren calc-silicate rock, which Seager referred to as garnetite. The deposits are tabular and dip west about 40 to 70 degrees, and have been explored by open cuts, shafts, and drifts to depths of about 200 feet. The primary ore minerals were chalcopyrite, sphalerite, and malachite, while azurite, chrysocolla, and hemimorphite formed in the oxidized zone that extends to the bottom of the workings.

A large body of chalcocite was also reportedly found at shallow depths in the easternmost ore horizon. Gangue minerals, which are waste minerals extracted with the ores, are mainly quartz, pyrite, hematite, and “especially garnet.” The mention of “especially garnet” is worth noting, as this indicates that garnet is likely a common mineral that can be found at these workings.

The area is also described in detail within a Geology M.S. thesis by Thomas Glover from the University of Texas at El Paso. This thesis, dated 1975, is entitled “Geology and Mineral Deposits of the Northwestern Organ Mountains, Dona Ana County, New Mexico,” and is available as an open file report from the New Mexico Bureau of Geology and Mineral Resources at https://geoinfo.nmt.edu/publications/openfile/downloads/0-99/63/ofr_63.pdf.

Formation Studies Draw Debate

Glover described the mineralization as occurring within the Permian Hueco Formation. The Lead Camp limestone described as the host rock by Seager can be considered to be within this formation, even though there is still debate over the stratigraphic nomenclature for the region. Glover noted that the garnet was andradite, which is an iron-rich garnet, and that diopside and wollastonite also formed as replacement minerals during the pyrometasomatic stage of mineralization. Glover described three shafts at the site, which he listed as the Roos, Zinc, and an unnamed small shaft. He said the main ore minerals were malachite, azurite, chrysocolla, and complex sulfides, and he also noted that chalcocite and massive sphalerite were also encountered in the Roos and Zinc shafts, respectively. The Roos, Zinc, and a small unnamed shaft are apparently the three shafts that are shown on the Organ, New Mexico, topographic map.

Another source with information on the Memphis Mine is also one of the earliest publications on the Organ Mountains. This is “Geology of the Organ Mountains,” which is Bulletin 11 of the New Mexico Bureau of Mines and Mineral Resources, by Charles Dunham.

The bulletin was published in 1935 and is available at https://geoinfo.nmt.edu/publications/monographs/bulletins/downloads/11/Bulletin011.pdf. Dunham said that the Memphis Mine was discovered prior to 1882 and that a small water jacket smelter was operated on the property. The last work was completed between 1927 and 1929 by the Memphis Corporation. The geologic description is consistent with the information reported by both Glover and Seager.

Before going to the area I also checked the land status of the area using the Map Viewer for U.S. Bureaus of Land Management (BLM) administered land in New Mexico, which is available at https://www.arcgis.com/home/item.html?id=7c417fa0eab24661bd5050c3113c580d. This mapping is based on BLM information and it is actually provided by ESRI.com. The map showed that the area has both land that is administered by the BLM land and private land.

Visiting the Memphis Mine

BLM-administered land is generally open for mineral collecting, as long as it does not have any active claims. Private land may or may not be posted, and it is often difficult to determine private land in former mining districts if the areas are not clearly fenced or posted as such in the field.

I first visited the site of the Memphis Mine in late December 2013. I visited the area with my brother-in-law, Mike, and my son, Daniel. We did not have a four-wheel-drive vehicle so we parked on the north side of County Road D087 and hiked to the mines. There were no gates, fences, or other signs indicating that mineral collecting or access to the mines was not allowed, and the boundaries of private land were not marked or fenced. We did not see any indications of any active mining claims. This hike to the mines was a short walk and we were soon on top of several mine dumps. We did not see any rattlesnakes, but it was undoubtedly too cold. This place will likely have a lot of snakes when the temperature is right.

The area had some concrete foundations, which must have been the foundations for the former mill or water jacket smelter that was reported to be on the mine site. The dumps had an abundance of minerals, and there were several signs of previous rockhounds, such as freshly broken and piled rocks. I noticed an area near the foundations that was covered with an abundance of white rocks, and closer inspection revealed these were pieces of coarse white marble. Much of the marble was nearly snow white. In addition to the marble, I found several pieces of coarse calcite.

Some of the other dumps had garnet-rich rocks. Most of the garnet was massive, but some small individual crystals could be found with some effort. The garnet was generally light brown to light green, which is typically the color of andradite. The rocks were extremely hard, and it was often difficult to break off the garnet-rich sections.

Some of the dumps had a lot of oxidized hard rocks that were mostly dark brown limonite. They were dense and had a high iron content. Malachite was also common on the dumps. The malachite was generally light to dark green and formed as a crust or coating on the rocks. Many of the rocks also had coatings of light blue chrysocolla. However, I did not see any deep blue azurite. I thought this was a great place to see garnet, marble, and malachite, and it was easy to reach from the highway.

Returning to Memphis Mine

We returned to this area on January 1, 2018. I came with my son, Daniel, and my daughter, Roberta, who were 23 and 21, respectively, so I was fine with them walking around the site. This time we had a rental four-wheel-drive Grand Cherokee SUV, and we were able to drive into one of the access roads to the site. There were still were no signs or any gates in the area of the mines. We drove about 500 feet on the access road and parked the car in a safe location. The road quickly became rough and I had no interest in damaging my rental car, which I have done on previous New Mexico trips.

The area was much the same as I remembered it from 2013. We walked past the old concrete foundation up to the mine dumps. The shafts were either caved in or had a wire screen across open holes.

The area of white rocks was still present, and I was able to find some nice pieces of coarse marble and some calcite. Some trace malachite was also present in this area. I soon walked up to the other dumps just south of the white rocks. The area had some relief, and the hiking was minimal, but it did not involve much distance from our vehicle.

During my first visit to this area, I saw some garnet near the mines to the south, and I hoped that could see some more again. The second time around I quickly found many examples with garnet. The crystals were not large, and much of the garnet was massive instead of individual crystals. The garnet was generally a resinous brown, but some of the garnet was also light green. We also found much more malachite on this visit as well. Most of the malachite appeared as surface coatings on the rocks and ranged from bright to light green.

Patent Mine Basics

After we finished at the Memphis mine and surrounding area, we drove north on County

Road D078. I saw some additional mine workings to the northwest, and we wanted to see if we could get to these workings. We were able to drive most of the way, but the road soon turned into a sandy arroyo, and I thought it would be better to park and walk. Some of the bushes on the arroyo brushed up against my car, and this can also cause considerable and expensive damage to a rental car. We then hiked to the mine dump on the side of a long hill.

This mine is reportedly the Homestake mine, based on the maps in Seager’s 1981 paper. This area also did not have any fencing or indications that it was an active claim. What it did have was lots of trash and signs that it was used for shooting. There were several shell casings and items that were riddled with bullet holes, so it was obvious that other people frequented the area, but for reasons other than mineral collecting.

Despite the mineralogical description of the Homestake mine, we did not find any minerals here. This was surprising as the workings were extensive, based on the size of the mine tailings. The minerals were much better at the Memphis workings. The Homestake mine is only worth a visit if you want to confirm for yourself that no minerals are present here or if you are in the mood for target practice.

According to the BLM map referenced earlier in this article, much of the area is on BLM land, but the two southernmost shafts shown on the USGS topographic map are marked as private land and this may be part of a patented mining claim. Information from Mindat at www.mindat.org/loc-4448.html indicates that the Memphis mine is within a patented mining claim, and this may be what shows up as the private land on the BLM Map Viewer.

Patented mining claims are claims for which the Federal Government has passed its title to the claimant, making it private land. These are common in many mining districts on BLM and U.S. Forest Service land, and the boundaries are often not marked in the field. The Homestake mine area is within BLM land.

Preparation and Planning Foster Great Adventure

As mentioned earlier, the boundaries are not marked in the field and it is almost impossible to tell where the private land begins. We did not come across any posted ground, active or inactive claim markers, or other restrictions to visiting or mineral collecting. If you visit the area, you can use the BLM mapping link listed earlier to better determine boundaries in the field. And if you decide to stay on the BLM ground, you will still be able to find garnet, calcite, and malachite that has rolled down-slope from the main part of the mine workings.

The best way to access this site is from U.S. Route 70. Take U.S. Route 70 east from Interstate 10, and proceed about 11.3 miles to the intersection with County Road D087. Proceed approximately 0.3 miles north, and then turn right into a rough, unpaved access road to the mine area, and park at the coordinates. If you do not have a 4WD vehicle, I suggest parking on the north side of County Road D087 at a small turnout on the north side of the road

This site is a great place to see skarn minerals like garnet and marble, and the malachite is a nice bonus. If you are in the El Paso-Las Cruces area, it is an easy morning or afternoon trip. Keep an eye out for rattlesnakes and loose rocks. While we did not encounter any issues with visiting the Memphis mine area, be aware that access and land status are always subject to change.

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