When you admire a nicely cut specimen of charoite, surely you wonder how and where it formed. It may come as a surprise to learn the rock consists of more than a dozen minerals. Additionally, the formation of this rock takes place deep within (as far as nine miles down) the earth’s crust.

Geologists do not have x-ray vision, nor have they been that deep into the earth, so how do they know what happens that deep in the earth’s crust? After all, the charoite rock and all others must be close to the surface so we can study them. What brought them to us is the crustal movement. There must be clues in deeply formed rocks that give away hidden secrets, telling us how far down into the earth something forms. The clues do exist and are present within minerals in such rocks. They are known as index minerals.

Products of Serious Heat and Pressure

Index minerals are not minerals listed alphabetically in a book. They are minerals Mother Nature forms deep in the earth, using incredible amounts of pressure and temperature so high it is hard to believe the numbers. I’ve been underground in mines where the rock temperature is nearly 150 degrees. The deep gold mines in South Africa are far hotter, but such temperatures are child’s play compared to deep crust temperatures and pressures.

For some index minerals to even form, the temperatures have to be hundreds of times higher than the boiling point of water. The pressure down deep has to be thousands of pounds per square inch, which is much greater than on earth’s surface, where atmospheric pressure is about 14.7 pounds per square inch at sea level. The pressure deep in the crust is so significant we don’t measure it in pounds per inch. We use millibars. One hundred millibars equal 14.7 pounds per square inch. Deep in the crust, the pressure is measured in thousands of millibars, so we write it as kilobars.

During metamorphic action, the pressure on rock can reach 50 thousand pounds per square inch. We know diamonds form deep in the earth where the earth’s lower crust and its upper mantle meet. In the lab, we make diamonds at 3,000 degrees Celsius and pressure that measures 50,000 pounds per square inch.

Such high temperatures are far greater than what is needed to melt rock. Molten lava runs around 2,000 degrees Fahrenheit. So why isn’t the earth’s interior primarily liquid? The pressure is the answer. The rock is under such high pressure it can’t expand to liquefy, so it is in a plastic-like state. With the rock in that state, mineral molecules move slowly toward each other. Given eons of time, this builds larger molecules, which can develop into discrete mineral crystal species that form under such high heat and pressure.

The result of all this is a suite of minerals geologists call index minerals because they only form within certain high temperatures and pressures when they crystallize. The mineral species present, in turn, tells us how high these temperatures and pressures were when these minerals formed. Later the rock is moved toward the upper crust through mountain building or continental movement and is exposed by weathering or mining and then found by rockhounds. It is the index mineral species that form at a depth that tell us charoite and other minerals, as well as the pegmatite formations, were once present. Such deep forming minerals help us understand the circumstances of where the formation of metamorphic rock occurs.

Before we could accurately estimate the conditions around metamorphic rock development using index minerals, we used other means to tell us what goes on beneath our feet. One primary source we still use is earthquakes, both natural and human-made. When there is a major earthquake, the earth vibrates, sending out waves of motion, and the entire earth shakes. As these waves encounter rocks of differing compositions and densities, the waves slow down, speed up, or turn, and we map them. By tracking and measuring waves, we have a pretty good picture of the earth’s interior and even its rock types. By creating our earthquakes with explosions or heavy surface pounding, we can generate the same waves, which helps us study the crust. But these actions do nothing to identify temperatures and pressures. Index minerals provide information that allows scientists to estimate temperatures and pressures as rocks go through metamorphism.

Metamorphism In Action

There are two general types of metamorphism, regional and contact. The latter is what we might say is localized since it occurs in existing rock formations like limestone when invaded by a hot igneous formation. The pressure and heat of this intrusion have a dramatic effect on the rock. Hot solutions, coupled with re-crystallization of the invaded rock, can create an entirely new suite of minerals. For instance, when heat and pressure impact limestone, it re-crystallizes as marble, and a different suite of mineral species may develop.

Regional metamorphism is much more insidious and extensive. It develops over vast areas of rock because of continental collisions, mountain building, or other major geologic events on a broad scale. This action and resulting mineral development are exceedingly slow and long-lasting, almost never-ending. Within such activity, many different mineral species develop, many of them not particularly attractive or colorful. They remain locked in the host rock and rarely appear free-standing.

You may ask how discrete crystals can develop when they are locked in solid rock. During extreme metamorphic action, the rock is not stable, but in a plastic-like state in which fluid-like mineral molecules can slowly move, accumulate, and develop crystals. Regional metamorphism can continue for millions of years and is still happening as continents drift, giving mountain-building minerals plenty of time to form. The slow and inexorable pressure and heat produce a group of minerals called aluminosilicates.

These are minerals whose composition is aluminum, silicon, and oxygen, usually with metal element impurities.

Among the aluminosilicates are three polymorphous examples that form in metamorphic rock and are categorized as index minerals; these are sillimanite, kyanite, and andalusite. Polymorphs have the same chemical composition but form in different crystal systems or different internal crystal structures. The two index minerals andalusite and sillimanite form in the orthorhombic system but differ internally. They also tend to form at the higher end of the temperature and pressure ranges during metamorphic action. The index mineral kyanite can develop in an even more extensive range of temperatures and pressures than the other two, so it may be present in both contact and regional metamorphic rocks. By studying these three minerals in a substantial rock formation, geologists can determine three things about the composition: The depth where it formed, the temperature during development, and the amount of pressure present.

Understanding Sillimanite’s Rarity

The three polymorphous minerals we’re examining each form in various temperature ranges. Andalusite forms in 200 to 800 degrees Celcius, but only if the pressure is low. Kyanite forms in the broadest range of these two factors and thus forms quite often. Sillimanite, on the other hand, forms under the most pressure, but only if the temperature is above 800 degrees Celsius.

Sillimanite is not a particularly attractive mineral. It is usually fibrous and gray-brown, sometimes with a pink tint. The mineral was first identified in Chester, Connecticut, and named after Yale Professor Benjamin Silliman, who played an essential role in the emergence of the science of mineralogy. Sillimanite is rare, and you’ll probably never see any crystals for sale, except an occasional example mined in India. However, it is mind in various locations, specifically for industrial uses. My old 1948 Plymouth used spark plugs probably made using sillimanite because it is a superb refractory, a substance that can withstand high heat. Furnaces, kilns, and other high-temperature equipment are lined with bricks or tiles often made with sillimanite.

Interestingly, when the legislators of the great state of Delaware were looking to designate a state mineral, they chose sillimanite.

Andalusite’s Uncommon Formation

Andalusite does develop crystals, which tend to be a little odd because, in cross-section, they are perfectly square. The crystals grow in metamorphic schist, most commonly formed as sedimentary shale. Again, andalusite can resist high heat, so it is part of the production of refractory tiles, bricks, and ceramic materials. It will actually convert to sillimanite if the temperatures are raised high enough.

The first andalusite crystals reportedly appeared in Andalusia, Spain, in 1789. Industrial quantities of andalusite are allegedly typical in South Africa as well. The most unusual occurrence of andalusite occurs in mica schist, where the square crystals twin and form a cross. Repeated andalusite twinned crosses in mica schist is used as a decorative stone or cut in a cabochon gem shape. In the twinned form, this mineral has a different name, which is chiastolite.

Kyanite’s Market Prevalence

Of the three index minerals discussed, the one seen most often at shows and in displays is kyanite. It is difficult to imagine, but of the three index minerals listed here, kyanite forms deepest in the earth, where pressures can read over four kilobars. Yet, it is the only one of these three minerals that form in pegmatite deposits, in beautiful discrete prismatic crystals, with lively deep-to-light-blue coloration, due to minor metallic impurities.

In rare instances, kyanite can even appear green, due to iron, and orange when levels of manganese are present. Although green and orange examples are often cut into gems, it’s a challenge to accomplish, since kyanite is anisotropic.

Anisotropy is the property in any mineral presenting with two different levels of hardness in the same crystal. If you scratch a kyanite crystal across the long crystal axis, the hardness is 7, which is close to quartz. Scratch it the length of the long crystal axis, and the hardness is 5 to 5.5. Other minerals show anisotropy, but not to the same extreme as kyanite. Kyanite appears in long slender blade crystals, which are usually several inches long, and a fraction of an inch wide. Specimens are common in Switzerland, with the finest examples hailing from Brazil.

Kyanite also often accompanies crystals of staurolite, which is a popular iron, magnesium, and aluminum silicate, a metamorphic mineral that frequently forms in cross or X shaped twins.

Of the three index minerals, only Kyanite is truly attractive and colorful, and should undoubtedly appear in your collection. In reality, all three should, because as major index minerals, they make for good conversation when you talk about the role played by index minerals.

This story about agate formations previously appeared in Rock & Gem magazine. Click here to subscribe. Story by Bob Jones.

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

Willemite and Franklin-Sterling Hill Connection

Mention willemite to any collector, and, likely, they’ll instantly think of Franklin-Sterling Hill, New Jersey. That’s because these are the only deposits where it is the primary zinc ore.

It is no accident that Franklin, New Jersey, is the “Fluorescent Mineral Capital of the World.” After all, the twin complex zinc-iron deposits of Franklin-Sterling Hill have managed to produce something over 70 minerals that respond to some form of ultraviolet excitation. But you have to wonder if Franklin would be so honored to be this specific capital if willemite did not respond to ultraviolet excitation.

The fluorescence of this zinc silicate is so dependable at Franklin that ultraviolet light is present on the picking table to beneficiate the ore as it comes to grass. Willemite’s importance in New Jersey is its zinc content. The two New Jersey deposits of Franklin-Sterling Hill were the only major producers of that useful metal.

Finding Willemite

The discovery of willemite took place in a small locality near Altenberg, Belgium. When found, it was described as a siliceous silicate of zinc and later named for Belgium’s King William I.

The New Jersey deposits were known to the indigenous peoples before Europeans arrived. When Europeans came to the region in the 1600s, the Dutch were said to be in control, but evidence of their mining activity is sketchy at best. During the 1700s, serious mining started but not for zinc, as open-pit methods were used to mine small deposits of magnetite. The iron ore was smelted in small furnaces that gave rise to the original unofficial name, Franklin Furnace.

The men who served as the first smelters made attempts to include the abundant complex ore franklinite, but the zinc content gave the men fits, as it formed completely useless slag-like remains. It wasn’t until the mid-1800s that studies of franklinite ore resolved the smelting problems, and zinc mining could commence in earnest.

Willemite’s Fluorescent Properties

Willemite can be a significant fluorescent mineral. Under short wave ultraviolet light, it often appears as a brilliant green. The response only diminishes when there are differences in the impurities in the zinc silicate structure. The chromophore manganese causes a fluorescent reaction.

Willemite’s almost constant companion in the New Jersey region, calcite, responds to the chromophore presenting as bright red. The percentage of manganese impurity in these fluorescent minerals determines the strength of the response. About three percent of manganese in the structure gives the ideal result. Iron has the opposite effect, diminishing the fluorescent response.

Willemite Shapes

Usually, while showing rhombohedral terminations, willemite crystals form in a hexagonal shape. Small gemmy crystals are also found in a few localities, like Franklin and the original European source, and they are often colorless and usually prismatic. However, such crystals are uncommon at Franklin-Sterling Hill, as the New Jersey crystals are often crude and opaque. In this region, most willemite has formed in Franklin limestone and marble, and have been etched out or chipped to expose their complete form.

Willemite is found abundantly in this locale in a dozen different forms, ranging from small and gemmy as uncommon textbook crystals in narrow seams to big ugly rounded crystals embedded in calcium carbonate. This mineral is also prolific in solid veins, chunks, masses, and even small isolated spots in the ore. Because of its response to ultraviolet, it is easy to spot.

Willemite Colors

In terms of color, willemite exhibits a range from colorless, pale green, and yellowish in nearly perfect small crystals to pale green, green, dark green, red-brown, even black in the large crystals and masses. Yet, when one thinks of willemite crystals, what comes to mind immediately are big, slightly rounded blunt hexagonal crystals with rough prism rhombohedral faces that are some shade of red or reddish-brown, due to iron in the structure.

Willemite or Troostite?

For decades the red-brown willemite crystals from the New Jersey deposit have been referred to as troostite. While troostite is now a discredited mineral name, it does have a historical connection to identifying additional minerals in Franklin. G. Troost, a researcher who studied Franklin minerals and published several articles on the topic, concluded that all of the large-sized red minerals from Franklin were a specific mineral.

Eventually, they became known as troostite. The name stuck even after scientists sorted things out and showed the red crystals were willemite.

Exploring Sterling Hill – A Personal Story

After the mines in this history-making area closed, this writer was privileged to travel deep underground at Sterling Hill for a collecting excursion, before the groundwater rose and nearly filled the mine. Shutting off the pumps allowed groundwater to rise, slowly sealing the lower workings forever. During my visit in 1987, one of the owners, Dick Hauck, escorted me underground to collect, which included descending to the 1,800-foot level. We had to use ladders to descend into the mine since the incline haulage equipment was not available. Dick and his brother, Bob, purchased Sterling Hill mine at auction and turned it into a fascinating museum.

At the 1800-foot level, we were able to see the water level in the next level down, but we had plenty of time to explore and collect. With only a hammer, chisel, and ultraviolet light, I was able to locate a nice small vein of calcite-willemite and chop out a few pieces of ore, remembering I had a 1,800-foot vertical climb to make to reach daylight. That was quite a fun trip!

Finding Willemite Specimens

A fascinating feature about Sterling Hill is the exposed wall of the surface property. These deposits were well known because of the indigenous peoples and later arriving Europeans who were exposed to the ore veins. Lighting one outside wall with ultraviolet shows a marvelous streak of fluorescent minerals.

Though both mines are long since closed, collectors still find success in locating good specimens by working the remaining dumps in the mining area. A small digging fee is required, but the dumps are still fruitful from decades of active mining.

While there’s no question willemite is a popular and prolific mineral in the Franklin-Sterling Hill deposit; it’s also present in many mining localities. Although any deposit rich in zinc might produce willemite, it is just a minor product of weathering. Using shortwave portable ultraviolet lights while checking several well-documented silver mines in Arizona, willemite often shows up intimately associated with other minerals, like red fluorescing calcite, blue fluorescing fluorite and even some types of clay.

Willemite Mined In Tsumeb

Another major source of willemite was Tsumeb, Namibia. Tsumeb willemite differs markedly from that of the New Jersey species. Tsumeb willemite does not fluoresce. There are also no records of large crystals, and many assume the willemite in this locale is all secondary, unlike New Jersey, where much of the zinc silicate is considered primary.

Tsumeb is unique because the deposit has three separate oxide zones because of North Break Fracture. This huge fault brought atmospheric oxygen and surface moisture deep underground, resulting in an attack of the primary sulfides. Also taking place at this time was weathering of the ores, which created a wonderful array of superb secondary species, including willemite, and even more importantly, smithsonite. Germany took over operations of the mine in the early 1900s, only to lose it after World War I.

When Tsumeb crystals were found, they were seldom as much as a centimeter long, and their color ranged from white to yellow. Generally, the willemite found in Tsumeb is white in small needle sprays within tufts on a matrix. Occasionally the needles reach a centimeter but are usually smaller. Another form of willemite appears in rounded or curved surfaces, and sometimes as complete balls. These can be of different colors from green to bluish.

Standing out from the Crowd

Without the specimens from Franklin-Sterling Hill, willemite would only be another unusual species and not the major collector species we enjoy. Only from New Jersey does it cause great interest, curiosity, and even excitement among collectors because of its colossal crystal size and brilliant red and green fluorescent crystalline masses of calcite and willemite.

While the Franklin, Sterling Hill deposits are the subject of several studies, admittedly, the most accurate and complete research of the deposits was done by Dr. Peter Dunn, noted researcher based at the Smithsonian Institution. Frequent interviews and discussions with locals, miners, and collectors, helped Dr. Dunn assemble an exceptionally comprehensive group of texts on these complex and historically essential deposits. For students of fluorescent willemite and the Franklin-Sterling Hill zinc deposits, Dr. Dunn’s work is the most comprehensive research work available.

This story about willemite previously appeared in Rock & Gem magazine. Click here to subscribe. Story by Bob Jones.

The post Meet Willemite a Fluorescent Beauty first appeared on Rock & Gem Magazine.

Many specimens may carry the name axinite. But in actuality, axinite describes a group of similar and closely related but slightly different minerals.

According to information at www.minerals.net, the general composition of axinite is that of a basic aluminum boro-silicate of calcium, iron, magnesium, and manganese. The minerals that compromise this group are axinite-(Fe), axinite-(Mg), Axinite-(Mn), and Tinzenite. The Mineral of the Week is a specimen of axinite on offer at mineral-auctions.com. 

The name itself is inspired by the presentation of the sharp-edged crystals, similar to that of an ax, or in Greek terms, axine, which is what inspired the name of this mineral group in 1787. Sometimes, the crystal also appears in groups of rosettes of sharp crystals instead of a singular columnar blade or blades.

In terms of coloration, axinite specimens are known to be dichroic, meaning revealing different colors when viewed at different angles. The most common colors are smoky brown, purple-brown, greenish-brown, gray, and even black. Among the less common but still reported axinite colors are green, purple, orange, and yellow.

This week’s featured specimen of axinite [axinite-Fe] was discovered in the Canta Province, Lima Department, Peru. According to information in the lot description at mineral-auctions.com, it presents as a root-beer brown formation of wedge-shaped, sharp crystals. An interesting point of the crystal is what appears to be arrowhead growth patterns. The specimen is rather substantial in size, measuring 10.2 x 9.1 x 4.9cm and 338 grams.

The specimen is offered for auction by Joe and Michelle Weisberg via mineral-auctions.com. Learn more and bid: http://egmediamags.com/url-tracking/tracking?id=OEhnQkErMEJ5MWRjNWdwMkhwNEp4dz09

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

By Antoinette Rahn

Time and again, when I’m researching or considering the evolution of rockhounding and lapidary equipment, I’m reminded of the quote largely believed to come courtesy of Plato that states, “Necessity is the mother of invention.”

Such appears to be the case when it comes to the development of the modern-day rock tumbler. As various records state, it was the mid-20th century when a jeweler, Edward Swoboda, found himself with a hefty supply of stones, including tourmaline and beryl, but rather few of that supply were quality pieces, so he took to cutting and polishing the stones into an unusual shape, baroque in nature. From there, he made small items of jewelry, including brooches. From a less-than-desirable shipment of stones, Swoboda turned “lemons” into popular “lemonade.”

Inspiring Innovation

The necessity part came in when the jeweler realized that, with the influx of orders, he would need a much faster process to get the stones to the point where he could cut and create the newest thing in gemstone jewelry. As records reveal, he teamed up with Warren Jones to design and engineer “a mechanical means of finishing the stones,” according to an article in the Lapidary Journal.

As is often the case when something of success comes to be, others soon dove into the world of rock tumbling equipment, and a variety of manufacturers formed operations, including Herb Walters and his team at Craftstones. The company formed in 1953 and became a significant “producer and wholesaler of tumbled stones.” Before the company leaped to global status, their method was clear cut, using paint cans and 10 pounds of stone. Eventually, after hours of refining and engineering, the tumblers used by Craftstones grew larger, as did the demand for polished stone, and today the company’s operation relies on various types of tumblers, including enormous 6,000-pound tumblers located and operating in South Africa, according to the Craftstones website.

Individual Interests Rise

While the industrial-level tumbling equipment and efforts continued to develop, there was equal interest among individuals to lay their hands on the devices that help turn rough into polished stone. Within a few years of Swoboda and Jones’ engineering feat, dozens of companies were selling tumblers and related supplies. With many companies in the game of rock tumbling, the spirit of innovation was ever-present, and the type of material used for the tumbler changed and evolved. From metal cans to a tumbling barrel made of old automobile tires to plastic barrels, the first quarter-century of rock tumbler history was marked by progress and improvement.

Yet, as is often the case, popularity and economic conditions changed, and a number of the companies that came to fruition to serve the growing interest in rock tumbling ceased to be in operation by the fourth quarter of the 20th century, with the exception of two of the earliest rock tumbling companies, Lortone and Thumler’s. Both went into operation in the 1950s and are still serving rock tumbling enthusiasts with dependable equipment that has truly stood the test of time.

Even with the ebb and flow of popularity, we continue to see interest in rock tumbling among all ages and interests of rockhounds and lapidaries. It’s a hobby that continues to attract new fans and satisfy its long-time enthusiast’s interest and needs. It’s a good thing indeed that sometimes necessity is the mother of invention.

About Kingsley North: Kingsley North has provided equipment and supplies to lapidary artists and jewelry makers since 1977. The family-owned business, headquartered in the stunningly picturesque western corner of Michigan’s Upper Peninsula, is the product of dreams, hard work, and dedication of founder John Paupore Sr. and family members.

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The post Tumbling Talk: Modern-Day Marvels and Righteous Rough first appeared on Rock & Gem Magazine.

I’m a bit of a sucker when it comes to green minerals and gems, especially when the description includes mention of “apple green” color. Perhaps it’s the Irish heritage I possess that draws me to green minerals and gemstones; I’m not sure. Regardless, when I saw the ludlamite specimen shown here listed among the minerals for auction through mineral-auctions.com, I was captivated.

Another striking feature of this and most ludlamite specimens is the prismatic crystal habit. There is something about prisms that draws me in and leaves me wondering what path the mineral had taken to get to where it was at that moment that I saw it. Typically, ludlamite, which is considered a rare phosphate mineral, is found in granite pegmatites. This fact speaks to its discovery in the Wheal Jane mine of Cornwall, England.

The discovery of this dynamic mineral belongs to the man after whom it is named, Henry Ludlam. Ludlam discovered the mineral in 1876, according to information at gemdat.org.

The next time you come across an apple-green mineral, be sure to take a few minutes to admire its beauty and composition. You never know; you may be staring at the uncommon ludlamite.

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Footprints from the Ice Age have long been found in spots around White Sands National Park in New Mexico. The area once hosted a huge lake, and the prints are found along what would have been muddy shoreline flats. Most often, these are animal tracks, including quite large ones left behind by mammoths. After enduring thousands of years, they frequently deteriorate and crumble away not long after exposure to the elements.

Fortunately, a new set of tracks reported in a recent issue of the journal Quaternary Science Reviews was found and analyzed when still relatively freshly exposed on the surface. The tracks are over 10,000 years old and extend nearly a mile, making them the longest human trackway found to date from the Ice Ages. And they seem to tell something of a little story.

Revealing Possible Scenario

The footprints show a person (suspected to be a woman due to the prints’ size) walking out along the lake and back and occasionally slipping on the slick mud. She could be excused for slipping because she cradled a young child on its hip. The depths of the prints are uneven.

Here and there, the left foot seems to be more deeply imprinted than the right foot, suggesting that the woman shifted her child from one hip to the other as she walked. How do we know for sure she had a child with her at all? Because at several places, small prints that might fit a three-year-old suddenly march alongside the larger prints.

Based on the length of the strides, researchers say the pair was in a hurry. Why so?

At spots, the fossilized human prints are crisscrossed by prints of gigantic mammoths and ground sloths. Perhaps Junior wanted a visit to the Pleistocene Zoo, but Mom noticed no fences separated them from the wildlife? Time to hurry back home, Junior!

The post Footprints in Time Tell an Intriguing Story from the Ice Age first appeared on Rock & Gem Magazine.

This Cambrian trilobite is found in the Wheeler formation of Delta County, Utah. Interestingly, it is quite uncommon to find this trilobite with free cheeks attached. Most examples appear as discarded molt because, with a hard exoskeleton, this trilobite species tended to molt to grow.

The BATHYURISCUS fimbriatus would split at the free cheeks and swim away to grow and harden its new exoskeleton. The cephalon, when found complete, is expanded forward and roughly semi-circular. It ends in small genal spines, which are the only spines on this species. The central or axial lobe is quite thin, and generally, this trilobite has nine body segments with a pygidium or tail that is fairly wide and flat.

This Cambrian trilobite often measures greater than two inches.

DID YOU KNOW: Trilobites, an extinct form of arthropod related to insects, crabs, crayfish, and horseshoe crabs, are among the most prevalent invertebrates with hard body parts to appear during the Cambrian Period. These creatures are called trilobite due to the three distinct “lobes” running vertically through the body section.

About the columnist: Joseph “PaleoJoe” Kchodl is a paleontologist, educator, veteran, author, fossil dig organizer/guide, business owner, husband, father, and grandfather, and fossil fanatic. For decades, he’s spent hours in classrooms around the Midwestern United States and beyond, speaking to school children about fossils and fossil hunting. Visit his site to purchase fossils, contact PaleoJoe, visit www.paleojoe.com.

Plus, learn more about PaleoJoe and his daughter PaleoJen and their paleontology exploration partnership in an the article “Fueling a Passion for Paleontology“.

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The post Molting and Moving — BATHYURISCUS fimbriatus Trilobite first appeared on Rock & Gem Magazine.

CALYMENE niagarensis is a very common Silurian trilobite found in the Rochester Shale. 

The trilobite is roughly triangular with a cephalon that is roughly semi-circular in shape. This trilobite is fairly broad, has a small pygidium, and presents with a thick exoskeleton. The thorax has 12—13 body segments. 

Many species of the CALYMENE appear around the United States, each differing a bit in body structure, size and shape. The niagarensis species is usually just over one inch in length. Examples of this trilobite are common in the area around Middleport, New York, and on occasion, in the Niagara gorge. 

Trilobites, an extinct form of arthropod related to insects, crabs, crayfish, and horseshoe crabs, are among the most prevalent invertebrates with hard body parts to appear during the Cambrian Period. These creatures are called trilobite due to the three distinct “lobes” running vertically through the body section.

About the columnist: Joseph “PaleoJoe” Kchodl is a paleontologist, educator, veteran, author, fossil dig organizer/guide, business owner, husband, father, and grandfather, and fossil fanatic. For decades, he’s spent hours in classrooms around the Midwestern United States and beyond, speaking to school children about fossils and fossil hunting. Visit his site to purchase fossils, contact PaleoJoe, visit www.paleojoe.com.

Plus, learn more about PaleoJoe and his daughter PaleoJen and their paleontology exploration partnership in an the article “Fueling a Passion for Paleontology“.

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The post CALYMENE niagarensis Carries Commonality to Unique Localities first appeared on Rock & Gem Magazine.

Seeing what you are doing while making a cabochon is as important as what you are doing with your hands and the machine you are using. It’s not only the brightness of your lights, but the type of light you are using that makes a significant difference in the quality of your work.

At my workplace, I use a long reach goose-neck style lamp. The best source for the lamp, in my opinion, is the popular Swedish home furnishings store. They call them luminaires. They come with a small wattage bulb that will not work for our purposes.

Selecting the Best Lighting for The Job and Space

Most new lighting comes with LED lamps, but they give out a diffused light, which is bright, but you can’t see details about the cab’s surface. In the past, I used clear 100-watt bulbs because they give out a spot of light that reflects off the surface and exposes the scratches and flat spots. Unfortunately, they are no longer available. As a replacement, I went to a clear 100-watt halogen bulb. These are difficult to find now, but it is possible to find them from time to time, for as little as $2 each. This type of bulb gives off a spotlight. One of the best sources of a spot-type light is the sun when it is available.

The next type of light that I find very valuable for detecting flat spots and contours on the top of the cab is a standard two-bulb four-foot fluorescent light fixture. I’ve mounted it on the ceiling with the bulbs aligned right-to-left in my workspace to reflect two parallel white lines across the cab’s surface.

Now let’s look at how lighting makes a difference. When working on a cab, and you have finished the grinding and are starting the sanding process, you can hold the cab in front and look at the two reflected lights. Ideally, you should see two parallel lines of light as you rock the cabochon back and forth.

Most likely, the lines will be jagged because of the flat spots remaining from the grinding steps. As you continue with sanding these flat spots, be sure to continue checking the reflections. When you see two straight lines, you have succeeded in removing the flat spots.

Lighting Aids in Checking Surface Condition

The next cabbing step is to remove the large flat spot in the center of the cab if you are intending on having a continuous dome across the top of your cab. I use a very coarse (80 to 100 grit) belt to sand the flat spot out. You want the two reflected lines to remain parallel across the top of the cab. This indicates that you have successfully removed the flat spot.

I also use the parallel light reflections to check that the top outer surfaces are smooth all the way to the edge of the cab. Any ripple will show up easily.

My final step occurs at my photo station. It has two LED spotlights. I shine one from the side to do the overall lighting and the other a little to the front, so I get a slight reflection on the edge. This is to indicate the quality of the polish.

The post Shed a Little Light on Your Cabochons first appeared on Rock & Gem Magazine.

By the late 1950s, exploration geologists in the western United States had spent a decade searching unsuccessfully for new sources of beryllium, an uncommon metal urgently needed for an increasing variety of uses.

Beryllium, a relatively soft, silvery-white metal with a very low density, ranks 51st in crustal abundance and is about as common as tin. Although widely distributed, it rarely occurs in concentrations rich enough to mine. Elemental beryllium is an excellent X-ray window and neutron reflector; although only one-third as dense as aluminum, it is stiffer than carbon steel.

Beryllium had no uses until the 1930s when major advancements in X-ray, nuclear, and alloying technologies began to create demand.

By the 1950s, the metal had become vital for a variety of high-tech applications. Historically, beryllium’s sole source was beryl [beryllium aluminum silicate, Be3Al2Si6O18], which was obtained only from a small number of granite pegmatites. But most of these were already mined out, and the United States was forced to import beryl.
Then in 1959, a Nevada rockhound searching the remote expanses of western Utah collected some unusual, purple-and-white, chalcedonic nodules that he thought would make good cabbing material. Needing help with identification, he stopped by the offices of a mining exploration company. Although no one could visually identify the nodules, an on-site geologist decided to test them with a beryllometer, an early forerunner of today’s X-ray-fluorescence analyzers. To everyone’s surprise, the instrument detected beryllium

The rockhound had found these nodules in outcrops of altered tuff at Spor Mountain in Utah’s Juab County. Small amounts of beryl were known to occur in Spor Mountain rhyolite, but no form of beryllium had ever been found in tuff. Laboratory analysis of a nodule confirmed the presence of beryllium. Although, not as beryl, but as tiny yellowish, orthorhombic crystals of bertrandite [basic beryllium silicate, Be4Si2O7(OH)2].

Core drilling soon confirmed that there was indeed bertrandite-rich tuff at Spor Mountain—and lots of it. Groundwater had leached beryllium from nearby rhyolite formations and redeposited it within thick layers of porous tuff. It appeared as tiny, disseminated crystals of bertrandite. Although the tuff graded only about 1.0 percent bertrandite, it occurred as a three-mile-long, one-mile-wide deposit that was shallow enough for inexpensive, open-pit mining.

After mining began at Spor Mountain in 1968, the United States immediately went from a beryllium importer to an exporter. Today, after 52 years of mining, Spor Mountain remains the world’s largest known beryllium deposit and the metal’s sole domestic source. This site produces three-quarters of the 300 tons of elemental beryllium
produced worldwide annually.

Small, beryl-rich pegmatites are still mined in China, Mozambique, and Brazil. Together, these nations account for about 20 percent of global beryllium production. Driven by record demand, a single pound of refined elemental beryllium currently costs about $400.

While beryllium remains vital for many X-ray and nuclear applications, its most significant uses are specialty alloys with copper, aluminum, and nickel, mainly for aerospace applications. Because of the remarkable lightness and stiffness of these alloys, aircraft and space-vehicle masts weighing just six pounds can support 95 pounds of instrumentation. And because metallic beryllium polishes even brighter than silver, it is an ideal material for space-telescope mirrors.

Beryllium is also used in automotive air-bag impact sensors, supermarket laser scanners, and computer hard drives. Racing bicycles that cost $12,000 or more are built with aluminum-beryllium frames that weigh only 1.5 pounds. Lapidaries now refer to the purple-and-white chalcedonic nodules as “Tiffany stone.” The nodules led to the discovery of the Spor Mountain bertrandite deposit 62 years ago.

These nodules consist of purple fluorite, common opal, quartz, manganese dioxide, and small amounts of bertrandite. Although most are destroyed in mine crushers, small quantities occasionally become available at gem-and-mineral shows and rock shops.

The post Beryl, Beryllium, Bertrandite Serve Technology Well first appeared on Rock & Gem Magazine.