While viewing the front of the Brazilian agate slab, I spotted a much more interesting group of features that I could use to enhance the overall aesthetic of the piece. A three-inch circle would allow me to bring out all of the best patterns that the piece could offer. I sketched the circle and added a curved feature on the top so I could drill a hole for suspending the piece as a pendant.

Where do I get my project inspiration? First, this column pushes me out of my usual cab shape routine and into using different materials, shapes, textures, patterns or colors. I read a lot of books on lapidary and jewelry design and also subscribe to a couple of magazines that have current jewelry styles and materials such as blue gems and minerals. Sorting through my multiple boxes of slabs often triggers my imagination too.

MAKING THE SHAPE

Before and during grinding, I make sure to follow proper lapidary safety precautions. While grinding the piece to a preformed shape, I used a one-inch diameter Mizzy silicon carbide wheel run dry to shape the inside curves on the top section. I drew a line halfway up the girdle as a guide for shaping the dome of the cab. I used an ultra-fine Sharpie felt tip pen to draw the line.

After I finished shaping and sanding the front of the Brazilian agate cab, I turned it over and focused on the translucent area. It was to be enhanced and ultimately be the main focus of the cab. From the start, I intended to drill four holes in the back of the cab so they would show through from the front. I drew a curved line in the center of the translucent area so I could lay out the position of the four holes. (It gives more visual interest if the holes aren’t in a straight line and if they are varied in size from larger to smaller.) I also made sure that they were evenly spaced between the holes.

DRILLING & FINISHING

I drilled small pilot holes for each bit and placed the bits in these holes to verify the correct spacing. I started drilling with a small coarse diamond bit. To get the best drilling action on the bits, I turned them on their sides. If you try drilling by placing the bit vertically, the very center of the bit does no work because it is spinning in one spot. By placing it sideways, the diamonds in the bit sweep across the cab and remove material.

I gradually stepped up in bit size and grit size until I reached the desired hole size. Because I wanted to ensure that the holes were highly visible from the front I drilled the holes up to 1mm from the front of the cab. I used an inside caliper to measure the 1mm depth. The final grinding step involved using a very large bit to chamfer the top edge of the hole to remove any chips.

The finishing steps were done with shaped wood bits using 220 and 400-grit tumbling media followed by shaped wood bits and cerium oxide polish.

The finished Brazilian agate piece came out much better than I had expected!

This story about Brazilian agate appeared in Rock & Gem magazine. Click here to subscribe. Story by Bob Rush.

Step By Step

The post Brazilian Agate Inspiration first appeared on Rock & Gem Magazine.

ABOUT MOROCCAN SEAM AGATE

Moroccan seam agate’s colors are amazing, just like the fall in New England. The colors range from red, orange, pink, peach and green. They are sandwiched between a basalt host stone, and the outer layers are mostly a mix of hematite and goethite. This creates a beautiful border, that at times, has a plume or even a paisley appearance. The majority of the inside of this agate will have a common range of color from red to orange, with decorative banding or fortifications.

HOW TO BUY

When purchasing Moroccan seam agate, you can easily see the patterns showing on the edges. This gives you a good idea of what the slabs will look like inside.

Most of this agate will range from 1/4-inch to two inches thick. This isn’t very thick and it can be a challenge to create shapes from it. What Moroccan seam agate lacks in size, it makes up in color and patterns. Most of the time it’s best to slab this material from north to south. If pieces are a bit thicker and show signs of agate pockets, these can be sliced horizontally, and you can accommodate a different pattern.

CUTTING MOROCCAN SEAM AGATE

The slabbing process is fairly easy with this material. Most of the pieces are like trimming the edges off of a slice of bread. I do all my cuts on a 10-inch trim saw.

Once Moroccan seam agate slabs are cut, this is where the challenge starts. Creating cabs with long thin narrow pieces can be difficult, at least to create a variety of shapes. I tend to choose large oblong ovals or marquise shapes for the majority of my cabs, however, you can get creative and find various ways to cut them utilizing the patterns in each slab. Always take into account that the very edges of each slab are softer grainy basalt that won’t be very good to leave in your cab design, so mark out each preform accordingly.

CABBING THIS MATERIAL

Once your preforms are trimmed out, the cabbing process is pretty standard for most agates. There are just a few things to note upfront.

The outer basalt rind should be trimmed off until you reach solid material, then grind your edges down to your preform marks.

The hematite/goethite edges might be a slight bit softer than the agate center. Don’t worry. This material won’t undercut, however, you will still need to closely watch your edges as cracks may appear as you start grinding down your girdle edge. They usually don’t go all the way through, they tend to show up, but only about 1mm deep. If this happens, you may have to alter your pattern slightly and grind that portion down or draw the edge of your cab in ever so slightly. You may also just shrink down your girdle edge and see if that makes it go away.

From this point, shape and dome on the 80 grit steel wheel. Once your shape is obtained, you can start smoothing out the top on either a 140 soft resin wheel or 220 grit wheel. This should remove the majority of the scratches. Next, finish sanding on the 280 soft resin wheel and continue to dry the cab off checking for any remaining scratches. It’s important to get all of the scratches out on this wheel before moving on since the 600 grit will not be able to get them out.

From this point, the remaining routine will finish off your Moroccan seam agate cab leaving a beautiful high polish on the 14k grit wheel and your cab is all ready to set into jewelry.

This story about Moroccan seam agate appeared in Rock & Gem magazine. Click here to subscribe. Story by Russ Kaniuth.

The post Moroccan Seam Agate: What to Cut first appeared on Rock & Gem Magazine.

WHAT’S IN A NAME?

Rock? Food? What’s up with the foodie name? Marketing! It’s kind of like a famous line from the classic movie, Spaceballs. “Merchandising, merchandising, where the real money from the movie is made.”

Grape agate is a fun marketing name for a fascinating mineral – botryoidal purple chalcedony. Plus, grape agate is easy to say, remember and visualize.

DEFINITIONS

Botryoidal – In Ancient Greek, this term literally means “bunch of grapes.” It refers to a mineral habit that is made of rounded segments. This habit is found in other minerals such as hematite, malachite, chalcedony, goethite, fluorite and smithsonite.

Chalcedony – The general term, chalcedony, refers to varieties of quartz where microcrystalline and cryptocrystalline crystals intertwine and grow together. There are many varieties of chalcedony in different colors and patterns. Chalcedony’s name is said to come from the Greek port of Chalcedon.

AGATE IDENTIFICATION FACTS

Grape agate appears as small, round nodules around two to eight millimeters across. Its colors can vary, ranging from translucent to a deep purple or lavender hue. It can also be white, gray, blue or green. (Maybe unripe grapes or the green kind from the store?) These vibrant colors are caused by traces of minerals, such as manganese and iron, that were present during the formation process.

One interesting feature of grape agate is its texture. The individual crystals that make up the grape-like clusters are usually small and spherical. They can have a bumpy or drusy surface, giving them a rough yet sparkling appearance.

When examining grape agate, you may notice tiny hollows or vugs on the surface. These are remnants of gas bubbles that were present when the crystals formed.

A NEW & RARE MINERAL

This is a newcomer appearing on the “rock” scene around 2016. Grape agate is found in only a few places on Earth — Indonesia and west of the Green River in Utah. It is a popular mineral for use as a display piece or in jewelry.

BEWARE OF MINERAL DUPES

Real grape agate is highly sought after and can be pricey depending on quality, especially the color and size. The deeper and bolder the color, the higher the price. And the bigger, the better. Beware though, some grape agate is dyed to achieve a more desirable color.

CARING FOR GRAPE AGATE

Grape agate has a Mohs hardness of around 6.5 to 7. With individual “grapes” sticking out, they can get jostled and come loose or fall off completely. Handle it with care and avoid contact with rough surfaces. When left in the sun, grape agate can lose its color so avoid setting it in a sunny spot.

This Rock & Gem Kids story previously appeared in Rock & Gem magazine. Click here to subscribe. Story by Pam Freeman.

The post Grape Agate: A Food Look-Alike Mineral first appeared on Rock & Gem Magazine.

Agate Facts

Agate has a seven Mohs hardness, making it desirable in the lapidary trade. Agate is translucent and exhibits a vitreous luster. As with other varieties of quartz, its chemical formula is SiO2. The name agate comes from the river Achates in Sicily and was given that name by the Greek philosopher, Theophrastus. Agate names can be derived from the location where they are found such as Botswana agate or Laguna agate or because of a feature they exhibit like lace, fire or moss.

How Agates Are Formed

Agate formation takes place when silica solutions fill voids in cavities layer by layer such as in Florida’s agatized coral. The voids typically are in solidified volcanic lava flows and the layering over long periods of time can result in different colors because of chemical changes in the silica solutions. The layering can deposit the chalcedony in concentric circles around the wall of the cavity or build the layers up from the bottom of the cavity.

Decorative Agates

Agate is used to produce cabochons, beads, and free-form objects in jewelry making. Book-ends, ashtrays, and sculptures are also made using agate.

Positively Agate

In the metaphysical realm, agate is said to change negative energy into positive energy and to heal anxiety and internal anger. Agate may also help with concentration and boost mental function.

Where to Find Agates

In the United States, agates are found in Oregon, Wyoming, Montana, Arizona, Idaho, California, Washington, New Mexico, Iowa, Wisconsin, Michigan, Minnesota, Utah, Florida, Colorado, Arkansas, and Nevada. Around the world, they are found in Australia, Germany, Brazil, Czechia, Botswana, Mexico, Morocco, Afghanistan, Argentina, Canada, Chile, India, China, and over 40 other countries.

This agate field guide appeared in Rock & Gem magazine. Click here to subscribe. Story by Richard Gross.

The post A Field Guide to Agate first appeared on Rock & Gem Magazine.

This is the first in a three-part series also covering types of gemstones with the letters J to R and types of gemstones with the letters S to Z.

What is a Gemstone? The definition of a gemstone isn’t quite as precise as the faceted beauties it describes. In general, when minerals, and sometimes organic materials such as amber, are cut and polished to create jewelry, we call them gemstones. There are nuances and outliers because some types of gemstones are too delicate to be worn, but most people in the gem world accept this general concept. To further clarify, types of gemstones are divided into “precious and semi-precious” stones with only diamonds, emeralds, sapphires and rubies encompassing the precious category. Everything else falls into the semi-precious zone, although this doesn’t necessarily imply inherent modern value or desirable characteristics. Regardless of the classification, there’s no question that when we can bring out the inherent beauty within these stones, it is something to be truly prized.

Agate

Agate is a silica-based mineral and is a popular semiprecious stone because of its attractive coloration and banding. Reportedly discovered by Greek philosopher Theophrastus roughly 2500 years ago, early people throughout the Middle East, Russia, and Greece used agates to create ornaments. According to research by the Bureau of American Ethnology, Indigenous People utilized them in much the same way.

Agate is a chalcedony, which is a type of cryptocrystalline quartz. Like many stones in this category, it’s created when groundwater seeps into the igneous rock where silica deposits form concentric layers within the rock cavities and crevices to create the telltale banded patterns.

The wide variety of colors, ranging from brown, black, white, red, gray, pink and yellow, are because of impurities in the groundwater. With a seven on the Mohs rating, agates are on the upper end of the hardness scale. This makes this translucent stone a favorite for rock tumbling. It’s often used for jewelry as well.

Bloodstone

An opaque, dark green type of gemstone, bloodstone features distinctive orange to scarlet red splatters that look like blood at first glance. This is the telltale signature of this traditional birthstone for March. The more modern birthstone choice is aquamarine.

Bloodstone is also called heliotrope, a name derived from the Greek helio meaning sun and tropos meaning toward the sun. If you garden, you’re familiar with heliotrope plants that turn toward the sun as they grow. This name indicates how the stone reflects the light. Along with legends of healing powers, bloodstone is also known as a protective stone. People will often wear or carry bloodstones to keep threats at bay.

The minerals chlorite and amphibole are responsible for the deep green coloration while iron oxide inclusions create the blood-red speckling.

Carnelian

Carnelian is one of the least expensive chalcedonies, the translucent yellow-orange to rich amber or even reddish-brown gems darken when heat treated. This includes the heat of the sun, so it’s best to keep your stone out of the sun to keep the color true. Iron is responsible for the red coloration and it’s what oxidizes and deepens when exposed to heat.

Carnelian is sometimes confused with jasper, although jasper is a type of gemstone that is typically a deep red and is opaque, rather than translucent. Plus, jasper often exhibits banding patterns on its surface appearance.

Carnelian is found throughout the world with some of the highest quality stones found in Scotland, Brazil and Washington State.

Even though it’s relatively inexpensive, many so-called carnelians are dyed and heat-treated agates. To determine if a carnelian is real, hold it up to the light. If it’s a natural carnelian, it looks cloudy. If it’s a heat-treated agate, it will most likely show striping.

Dumortierite

Although colors range from brown, green, and the rarer violet and pink, the eye-catching denim blue of this type of gemstone is probably the most popular with gemstone enthusiasts.

An aluminum boro-silicate mineral, dumortierite occurs in regions of high metamorphic activity that are also rich in aluminum and boron. Manganese, iron, and sometimes zinc inclusions, are responsible for the blue coloration.

Dumortierite was first described in 1881 after being found in the French Alps. It was named for the French paleontologist, Eugene Dumortier.

Dumortierite has a glassy (vitreous) luster. Its fibrous nature creates fine, almost hair-like radial crystals within the structure. The blue variation is sometimes mistaken for lapis lazuli, but dumortierite is typically a deeper blue or violet, plus lapis lazuli sports white or gold metallic flecks because of the pyrite within it.

Dumortierite quartz is quartz with inclusions of dumortierite.

Emerald

The birthstone for May, emeralds are a type of gemstone that earns their place as an adjective to describe a particularly intense green. The name is derived from the Greek word smaragdos, meaning green stone.

Created in metamorphic rocks when hot magma flowed over and through the crevices of limestone and shale, emeralds are a beryllium aluminum silicate. Although emeralds are a type of beryl, not all beryls are emeralds. While green beryl is still green, it’s distinctly lighter.

Chromium oxide is responsible for the emerald’s deep green. Other gems, such as peridot and tsavorite garnets, are also found in green hues but not with the same vibrancy. Registering 7-8.5 on the Mohs hardness scale and forming in hexagonal crystals, emeralds are long favorites for precious jewelry, but fakes abound. To determine authenticity, inspect the stone with a 10X loop. Flaws and inclusions, particularly a small crystal within the stone, indicate a natural emerald. Air bubbles or even a “too perfect” stone are tell-tale signs that it is not real.

Fluorite

Made of calcium fluoride, pure fluorite is colorless, yet samples are commonly found in shades of purple, golden-yellow, green, blue, pink and brown. These types of gemstones are translucent to nearly transparent with attractive banding. The term “fluorescence” became part of the terminology when physicist Sir George Gabriel Stokes was working with fluorite in 1852. Although fluorescence doesn’t consistently occur, fluorite is known to glow when there is the presence of uranium, yttrium and other rare earth elements. It often emits blue, although yellow, green, white and red shades are possible.

Also called fluorspar, it’s been produced in Illinois since the 1800s and is the state mineral. Often forming in cubic crystals, it is popular for jewelry but has a wide number of commercial applications ranging from an ingredient in ceramics to a flux used in refining metals.

Garnet

Many people picture garnets as red stones, but these types of gemstones are also found in shades of orange, pinkish-orange, green, reddish-purple, colorless and even blue and green, albeit these last two are rarer.

Garnets are formed when aluminum-laden sedimentary rock is metamorphosed. Garnets are one of the most widespread types of gemstones throughout the world. While the bulk of garnets is mined for industrial applications, it’s one of the oldest known gemstones and has been used for ornamental purposes for 5000 years. Historical evidence shows stones within the necklaces of pharaohs. Garnet signet rings were used by Roman leaders to seal documents.

Sometimes mistaken for a ruby, garnets are usually a darker red with brownish tones. When it’s held up to the light, yellow bands are often visible in a garnet while a ruby will be clear.

Hematite

Consisting of 70 percent iron, hematite is one of the primary ores of iron. Fortunately, it is one of the most abundant minerals on Earth. According to NASA, it’s also the most abundant mineral on Mars. The iron-rich environment is why Mars is dubbed the “red planet.”

Named as far back as 300-325 BCE, hematite is derived from the Greek haima, meaning blood. These types of gemstones are found in colors ranging from rust-red, brown, steel-gray to black, it always leaves a red streak when scratched on a scratchpad.

The distinct reddish hue has been used in artwork from the earliest cave paintings. It was a key pigment for Renaissance artists creating paintings with canvas and oil in the Middle Ages. Besides its importance as an ore for iron and in art, it effectively stops radiation making it useful in shielding applications. Plus, it creates a beautiful tumbled stone for those who love to collect them.

Iolite

This beautiful violet-blue stone was the secret to the Vikings’ success in crossing the ocean as they looked through a thin iolite specimen to determine the position of the sun on cloudy days. The key to this unique quality is called pleochroism where different colors are visible at different angles. For example, a piece of iolite may have the classic violet-blue hue on one side, but when it’s turned over, it appears yellow or clear.

A silicate of aluminum, iron and magnesium, iolite (also known as the mineral cordierite) is created in metamorphic and igneous rock formations. Derived from the Greek word ios meaning violet, some iolite is blue enough to look like a sapphire. Some speculate this quality is because of the presence of titanium, although iolites are easily distinguishable because of pleochroism.

This story about types of gemstones appeared in Rock & Gem magazine. Click here to subscribe. Story by Amy Grisak.

The post Types of Gemstones By Letter (A-I) first appeared on Rock & Gem Magazine.

Purchasing Ghost Fire Agate

Since this is a new material, it’s not readily available everywhere just yet, it can be found mostly on Facebook in some of the rock sales forums. When buying ghost fire agate, it’s best to buy from pictures that show at least one side faced, or cut in half, so that you can see what you are getting inside. This material has a great deal of matrix on the outside, and a greater portion inside. It’s best to see how much agate is there before committing to a price that might not yield enough usable agate area to cab since it’s purchased by the pound.

Slabbing Ghost Fire Agate

When starting to slab this material, I cut from two sides, north and west. This way I could see if there were drusy pockets or completely agate-filled nodules. I was able to choose which patterns I liked best. There is no definitive direction to load the stone in the vice, as there are no north-to-south types of patterns in this stone. Start off with the flat sides held tight in the vice. Once you get it cut, if there are large areas of the matrix in the center, I like to cut through them, and downsize the larger stones, so that I can cut smaller ones on a 10-inch trim saw. That way it’s much easier to switch directions with each slab cut, instead of continually loading a vice on the larger saws.

Once your slabs are cut, and it’s time to draw preform designs, you can include some of the matrix that’s still solid enough to cab and not worry about undercutting too much. I have noticed that the plumes grow from areas of the matrix, so I designed them in a way that the matrix is used as a partial framing of the cab. Other times, you can run into patches of beautiful purple and blue agate and isolate that as your cab. The other pitfall to look out for is the calcite that seems to border some of these areas. It’s much softer than the agate and will undercut fairly easily, especially if it’s on the edge of your cab.

Cabbing & Finishing

The cabbing process is fairly routine to most agates, but there are still several ways you can go to obtain the same results. Most lapidaries use a 6-diamond grit wheel setup. For those who still have, or use silicon carbide belts on a poly arbor, they seem to work well in the beginning stages as long as they are on two separate machines, and you rinse the cab off before going back to diamond grit, to keep from contaminating the machine with diamond wheels.

Start shaping and doming on the 80-grit steel diamond wheel. Once you have that portion done, you can continue to a 140 soft resin diamond wheel, or switch to a poly arbor set up, with 100 and 220 silicon carbide belts. The 100 will quickly smooth out the cab and remove all the deep scratches from the 80-grit. The 220 will completely remove any remaining scratches, making it quick and easy to finish the rest of the way on the diamond wheels, starting back on the 600, and all the way up to the 14k.

This story about ghost fire agate previously appeared in Rock & Gem magazine. Click here to subscribe. Story by Russ Kaniuth.

The post Ghost Fire Agate: What to Cut first appeared on Rock & Gem Magazine.

1. What is Carnelian?

Carnelian is a cryptocrystalline variety of quartz known as chalcedony, or agate. It ranges in color from yellow to orange to red and reddish-brown. Most prized are warm oranges and vivid reds. It forms as low-temperature deposits that fill seams, cracks or cavities and is often found as nodules. At Mohs hardness 6.5 to 7, with nice translucency and luster, it’s a fine lapidary stone.

2. Why is Carnelian Red?

The reddish-brown color of an old nail comes from iron rusting or oxidizing. Similarly, chalcedony is colored red if infiltrated by solutions bearing iron oxides during formation.

A caution! You may think you’ve found a beautiful red carnelian, but often a red exterior is only skin deep. When cut, the interior may be yellow. This reflects different concentrations of iron oxides that were in the solution as the nodule formed.

3. How Was Carnelian Named?

Per one source, “carnelian” comes from the Latin word carnis, or “flesh” because of its red color. Another source claims it comes from the Latin word cornum, referring to the glossy red cornelian cherry.

4. Is it Carnelian? Or is it Sard?

In ancient times, carnelian was referred to as sard. It is a gemstone mentioned in the Bible. The Roman naturalist Pliny the Elder said this referred to the Lydian city of Sardis in present-day Turkey. Others say it came from the Persian word sered meaning “yellowish-red.” Then there’s the Greek word sarx, meaning “flesh.”

Sard is russet-colored, or deep dark brown with a reddish-orange tinge. Remove the brown and you have carnelian. The difference between carnelian and sard is a matter of degrees, and the two names are sometimes used interchangeably. The amount of iron oxide influences the color range.

5. How Does Sardonyx Differ from Sard & Carnelian?

Forget carnelian versus sard. We also have sardonyx. This is a striped version of carnelian or sard with bands of white chalcedony alternating with red/brown stripes. Onyx is a Greek word meaning “nail or claw,” and sardonyx was said to resemble a fingernail with a white tip above a pink base. The stone has long been valued for the color contrast between layers.

6. I Bought a Red Stone. Is it Carnelian?

Dull light-colored chalcedony can be stained and dyed with iron salts. One source claims many stones sold on the market as carnelian are actually artificially stained chalcedony. Buyer beware!

7. Where Can I Find Carnelian?

It’s said the finest carnelian is from India, and the face of the Taj Mahal bears red flowers crafted from inlaid carnelian. But carnelian has been sourced from many nations including Brazil, Mexico, Saudi Arabia, Sri Lanka, Thailand, Australia and Germany. Material from Madagascar is currently prominent on the market. In the U.S., Oregon is notable, with nodules found on coastal beaches and in river gravels.

8. Did the Ancients Use Carnelian?

Because of its lush colors and ease in crafting, carnelian has been used in jewelry since at least the 4th millennium B.C. Carnelian beads have been found in Bulgarian grave sites from the Early Neolithic 8,000 years ago. In 2000 B.C., Egyptians used it for beads and cabochons, often set in gold alongside lapis. Ancient Greeks and Romans used it for intaglios (engraved stones) and set in gold as signet rings for sealing letters with wax.

9. What Lore & Legend Surrounds Carnelian?

The traditional birthstone for July is ruby, but one alternative stone is carnelian. The Zodiac birthstone for Virgo is peridot, but also carnelian. And carnelian shows up in Judeo-Christian religious traditions. For instance, high priests wore a gold filigree breastplate adorned with 12 stones, including sard, to represent the 12 tribes of Israel.

Because they were the color of blood, in ancient and medieval times red stones were considered talismans associated with life and were believed to attract the attention of good spirits while warding off evil. Carnelian was believed to calm tempers and to “still the blood” from rage. On the other hand, while stilling the blood, carnelian was also believed to promote courage in battle and to stir eloquence within shy speakers. Today’s New Age practitioners of healing stones say it purifies the blood, provides strength and soothes emotions.

10. Is Carnelian Still Used Today?

Just like the ancients, lapidary artists today value carnelian, whether slabbed and domed as cabs to set into earrings and pendants or to craft beads. It’s also carved and incorporated into intarsia. Colorfully translucent, hard and durable, and taking a glossy polish, carnelian has stood the test of time.

Rough or tumble-polished pieces make great display specimens.

This story about carnelian previously appeared in Rock & Gem magazine. Click here to subscribe. Story and photos by Jim Brace-Thompson.

The post Carnelian: Top 10 Facts first appeared on Rock & Gem Magazine.

Chalcedony

The general term, chalcedony, refers to varieties of quartz where microcrystalline and cryptocrystalline crystals intertwine and grow together. There are many varieties of chalcedony in different colors and patterns. They are plentiful and popular. Gem-grade chalcedony is generally light blue, white or gray and often called holly blue. Chalcedony’s name is said to come from the Greek port of Chalcedon.

Varieties of Microcrystalline Quartz

Agate – Curved banded variety

Jasper – Opaque, red or green varieties

Chert – General name used for compact, hard rocks that contain microcrystalline quartz

Flint – Afiner-grained, harder type of chert, Ohio’s official gemstone

Carnelian – Orange-red opaque mineral

Onyx – Parallel banded variety

Sardonyx – Red sard and white chalcedony

Chrysoprase – Translucent, apple-green color

Bloodstone – Dark green with red spots of iron oxide

Petrified Wood – Over time chalcedony replaces wood while preserving the growth rings

Happy Micro Quartz

Microcrystalline quartz has so many beautiful varieties that it’s often interwoven into our pop culture. It’s a happy birthday for these micro quartz birthstones – bloodstone (May) and sardonyx (August). Chalcedony itself is said to bring stability and balance to its bearer.

This story about micro quartz minerals previously appeared in Rock & Gem magazine. Click here to subscribe. Story by Richard Gross and Pam Freeman.

The post Micro Quartz Mineral Basics first appeared on Rock & Gem Magazine.

Beyond the formal definitions, agates are fun! They are common and abundant and can be collected almost anywhere. No matter where you live, there is probably an agate field within easy reach for a day trip.

Their abundance makes most agates inexpensive at rock shops and gem shows. Plus, they can be enjoyed “as is” or cut, crafted, and tumble-polished into lapidary wonders.

What are agates? The perfect stones for the beginning collector!

How are Agates Formed?

The best thing about agates is the variety they show in colors and patterns. An agate may grow as an undifferentiated mass. It may be all one color, or it may have inclusions or colorful concentric bands.

Agates precipitate out of solution and grow in seams within other rocks or within vesicles in basalt or cavities within limestone, later eroding out as nodules.

What are Agates? List of Common Varieties

While there are many, consider a few of the more common varieties.

Fortification agates have concentric bands that look much like a “fort” circling a castle.

Waterline (or water level) agates have straight bands that were formed by gravity as layer after layer of agate was set down.

Eye agates have spots on the surface.

Flame and plume agates are very similar. Flame agates have swirling red lines that look like fire, whereas plume agates have interesting inclusions that look like ferns or plumes of smoke.

Sagenitic agates have inclusions, but these are needle-shaped.

Moss agates are similar to plume agates, but the plumes permeate the entire rock, often in shades of green, brown, yellow, or red.

In addition, there are shadow, tube, seam, polyhedral, enhydro, fire, iris, and many more varieties of agates. This wonderful variety makes agates a whole lot of fun to collect!

Look through the agates in your own collection. How many varieties can you spot?

This Rock & Gem Kids column about what are agates appeared in the August 2021 issue of Rock and Gem magazine. Click here to subscribe!

The post What are Agates? Explore Common Types first appeared on Rock & Gem Magazine.

Within the roots, he discovered a few thundereggs, which lead him to further explore that area. There he discovered what would become his newest claim.

Since 2009, Jason Hinkle has owned and operated the mine and enjoys the rewards of mining his claim each year.

Fallen Tree Thunderegg Qualities

Fallen tree thundereggs are unique, with an outer rhyolitic shell, with mushroom rhyolite patterns, filled with various types of chalcedony (including agate), blue opal, quartz, and other inclusions. You never know just what you will get when cutting one in half!

Fallen tree thundereggs might not have all the prestige as many other Oregon thundereggs, but rockhounds and lapidaries will appreciate all the gorgeous variety that comes from this mine.

How to Purchase

When purchasing thundereggs, you can always buy precut halves to be able to choose the top-notch quality rock that catches your attention. But, there’s something to be said about the rush you get from cutting your own, to reveal a treasure that’s millions of years old and waiting to be opened. With any thunderegg, you never know what you’ll get until you cut it open. There are many times the inside will be a dud, and you have to keep cutting several until you get some good ones. This is to be anticipated.

Most of the thundereggs from this mine are generally baseball to golf ball size. Some lapidaries like to use the geode grab holder in the saw, but with these, I like to just cut them by hand on a 10-inch trim saw. You usually get the best results from cutting top to bottom, but experimenting with these can be a lot of fun. You can also yield various nice patterns by crossing-cutting.

Cabbing Thundereggs

Cabbing thundereggs is relatively routine, however, there are a few pitfalls to watch. The first is the differing hardness of materials. The outer rhyolite is much softer than the chalcedony centers. The rhyolite can also detach from the center agate, so stabilization treatments might be necessary before trimming out your preforms for it to hold together. There also might be a few fractures in the center, but you can always just work around those areas.

To start your cabs, trim out your preforms, and grind your shapes on the 80-grit steel wheel. Be careful doming the top being cautious not to break off any rhyolitic edges. Once the preforms are shaped, move onto either the 140 grit soft resin wheel or 220 soft resin.

At this point, dry off the cab thoroughly to check for scratches, any deep scratches should be removed by now.

Any micro-scratches can be dealt with on the next wheel.

Finishing Up

With material like this, I like to have a separate setup off to the side with silicon carbide belts on self-expando wheels. The silicon carbide belt smoothly removes scratches and is far less aggressive. This gives it less of a chance of breaking off any rhyolite edges and less undercutting from the hardness differences. From this point on, it should be relatively routine and easy, finish through your sanding wheels and polishing wheels and you can end at either the 8k grit or 14k grit wheel for a super nice polish.

This story about fallen tree thundereggs appeared in Rock & Gem magazine. Click here to subscribe. Story by Russ Kaniuth.

The post What to Cut: Fallen Tree Thundereggs first appeared on Rock & Gem Magazine.