Sunday, December 10, 2017

Cabbing soft stones

Have you ever wanted to make a cab out of a soft stone, but worried about ruining the stone in the grinding and polishing process?  Soft stones include such things as talc, gypsum, anhydrite, angelite, and even calcite.  One advantage of soft stones is that they are easy to cut and shape into whatever shape you desire.  Here I present the method I used to make an angel cabochon from angelite.

First, I rough cut the cabochon from the slab.  It was easy to cut fairly close to the shape I wanted even with the trim saw. 

Next, I finished cutting and shaping the angel with a diamond saw blade and stone shaping tool on a dremel.

Next, I ran the stone under hot water for 15 minutes.  This smoothed the rough edges fairly well.

Then, I used a 600 grit diamond wheel, very lightly for a short period of time to remove the scratches from my drawing the shape.  Then I moved to a 1200 grit diamond wheel until it was smooth.  Finally, I finished the polish with a 14000 grit diamond wheel.  None of these steps took more than a couple of minutes.  
Angelite finishes to a nice satin finish.

Finally, I wire wrapped the stone into an angel.

Dr. Janet Bertog, owner

Thursday, November 9, 2017

Using Butvar (polyvinyl acetate) for stabilizing stones

Sometimes it is necessary to stabilize rocks before cutting and polishing them.  Stones with fractures, porous stones or brittle stones will benefit from stabilization, allowing you to cut and shape them without risking the loss of the stone.  Typically, I hear of three primary methods of stabilizing stones.  I will summarize these methods below.  Then, I would like to introduce you to a material that is used by museums to stabilize fossils and artifacts.  This material, butvar, is a polyvinyl acetate and is used by museums because it does not deteriorate even after very long periods of time and it does not discolor.  It has an added advantage that it can be mixed to any consistency desired, so you can make a thin penetrant or a thick glue with it.  I have used this material to stabilize stones before cabbing them with success.

Typical methods of stabilizing stones

1.        Backing:  A backing is applied to stones, most commonly turquoise and opal, in order to keep the stone “natural” while holding the fragile material together.  Backing is simply applying a thin layer of material to the back of the stone that will help hold the stone together.  This mostly helps porous stones stay together and helps to keep stones together that have fractures.  Backing material varies widely.  Sometimes, a thin piece of stone is adhered to the stone.  Then the stone is cut and polished as normal.  Backing is not used if the back of the stone may be visible in the finished product.  Backing materials include basanite, black jade (typically a dark stone), or synthetic materials.  Devcon epoxy, an epoxy with metal in it, is sometimes used.  JB Weld, another metal epoxy, is also common.  A thin layer of the epoxy is applied and allowed to dry completely before the stone is cut and polished.

2.        Thin cyanoacrylate (“super glue):  Thin super glue can be applied to a stone with fractures or pits.  The superglue will fill the fractures and pits, holding them together.  While this method may work for fractures and pits, I have not had luck with using it to stabilize a generally fragile stone.  Most often the glue just forms a coating on the surface of the stone, which easily peels off during the cutting process.

3.        Epoxy Resin

Opticon resin:  I have heard mixed results about this material.  Some people swear by it, others hate it.  Opticon is a thin resin that is supposed to dry water clear, so it does not discolor the stone.  It can be used to impregnate a porous stone, so it fills a niche the first two methods do not.  It can be a little tricky to use.  For a description of using Opticon, see these instructions on the mindat website:

Standard epoxy:  I found reference to using epoxy dissolved in acetone on this discussion board:  Note that I read elsewhere that it says to use equal parts of epoxy and acetone.

Butvar Polyvinyl Acetate

There are a few different types of butvar that have different molecular weights.  The two most common are B-72 and B-98.  I have used both of these in my museum work.  Typically we used B-72 in fossils that were rather wet, but mostly we used B-98.  B-72 can be dissolved in alcohol or acetone.  B-98 should be dissolved in acetone.  Note:  Please use caution with these materials.  They are not toxic and they will not hurt your skin, but the acetone can.  The acetone is a known carcinogen and it is recommended that you wear gloves and eye protection when working with it.  Do not get it in your eye – you will glue your contact to your eye and it will scratch the surface of your cornea (sure, ask me how I know!!).  For the most part though it is very safe.  We use is all the time on fossils in the field and the lab.  I will mention a couple of different methods for using butvar to stabilize your rocks. 

1.     Mix a thin consistency of acetone and butvar in a container that has a lid.  There should be enough butvar in the container so that it will actually work, but it should still be water thin.  So add butvar, and if it starts getting thick, add a little more acetone to thin it back out.  The amounts are not critical.  You will want a large enough container and enough of the mixture to cover the stone you are working with.  Put the stone in the container.  Let it sit for several days, 4-7 is recommended.  During this time, It is advised to shake or  stir the container.  I found shaking most useful in order to stir the stone around in the container.  One option, which I have not done, but I plan to try at some point, is to put the stone in a container where you can add suction to it.  I am thinking like a space bag, where you put things in the bag then use a vacuum to suction it.  If you do this, you would want to apply suction to pull the butvar solution up, but NOT suck it completely out of the container.  Repeat this several times.  The advantage of doing this is that it will force the butvar into the stone and there will be less wait time. 

2.     What I found to be most efficient was to create a thin concentration of butvar in the acetone, it needs to be pretty thin the penetrate the rock.  Then I put the rock on a piece of plastic wrap and pour the butvar over it (this is the method we use in the field, especially when the bone is still in the rock and we can’t soak it).  I will do this, let the acetone evaporate, and continue doing this until is does not evaporate within about 10-15 seconds.  Then I know the butvar has penetrated as much as it can.  I turn the rock over and repeat on the other side.  Then I let it dry for a few hours.  I did not find it necessary, but it was suggested that if you heat the stone before applying the butvar it well help to open the spaces. 

I have a new material I collected from North Carolina, which I call Mountain Petronella.  It has very soft minerals mixed with hard minerals and they have a lot of planes of weakness in them.  I was not able to cab this material but when I stabilized it with butvar, it cabbed great.

Mountain Petronella from North Carolina

I also have a piece of granular peridot, which has individual grains that are very loose.  I was able to stabilize and cab this material as well.
Granular Peridot

Wednesday, October 11, 2017

Red River Gorge, Kentucky

In my other life, I am a professor of geology at Northern Kentucky University.  An important part of my teaching is taking students on field trips to expose them to geology first hand.  Last weekend I took my introductory class to Red River Gorge in Kentucky to study the formation of natural bridges and other associated rock formations.

Red River Gorge is near Slade, Kentucky, about an hour southeast of Lexington.  It is one of the largest collections of natural bridges in the country.  

Red River Gorge is on the edge of the Appalachian Plateau on what is known as the Pottsville escarpment.  In this area, sandstone from the Pennsylvanian Period, about 290 million years ago, is exposed.  This sandstone is relatively resistant to erosion, especially compared to the Mississippian Limestone that lies below it.  As a result, it holds up the edge of the plateau and creates the escarpment, where it drops down to lower elevations where the Mississippian limestone is exposed.  

From University of Kentucky department of Geography.  The blue-gray area on the east side of the state is Pennsylvanian sandstone and the lighter blue is Mississipian limestone.  

The region was uplifted along the edge of the Cincinnati arch during the formation of the Appalachian Mountains, which ended in the Permian Age, 245 million years ago.  The uplift warped the continent in this area and made the layers tilted, as shown in the geologic cross-section above.  This causes different rock units to be exposed in different parts of the state, with the oldest in the center of the Cincinnati arch, which is centered on Lexington, and younger rocks found in a bulls-eye pattern around it.  Where the Pennsylvanian sandstone and the Mississippian limestone are exposed together, we get the escarpment.  

The flat tops of the hills are the Appalachian Plateau.  The Red River cut down through the sandstone, exposing it and allowing the formation of the natural bridges.

The limestone was deposited in a shallow sea teeming with life of a coral reef in a shallow sea that formed in the Appalachian Basin, a low area that formed when the Appalachian Mountains pushed up and put weight on the continent, pushing it down.  From the Mississippian to the Pennsylvanian, this basin started to get more shallow and the sandstone was deposited in layers by large rivers flowing off the Appalachian Mountains and into the Appalachian Basin.  During the uplift of the Cincinnati arch, the sandstone was fractured in both a north-south and east-west direction.  

The combination of horizontal layers in the sandstone and the fractures are responsible for the formation of the natural bridges in this area.  Initially, the sandstone starts to weather by grains of sand and pebbles getting plucked out of the sand.  Small holes open up in the sand, and the grains get caught up in the holes with wind and rain and tumble around in the holes opening them larger.  This creates a "swiss cheese" texture in the rock.  
"Swis cheese" texture in the sandstone as little holes open

Eventually, these little holes grow to where they start combining together and open up recessed caves.  Recessed caves are shallow but long and follow the layers in the sandstone.  The layers are zones of weakness in the rock, so the rock weathers more quickly here.  

A recessed cave can be seen under this waterfall at Rock Bridge
The sandstone has horizontal layers that are more susceptible to weathering and open up recessed caves
Because the sandstone is fractured vertically, eventually, the recessed cave will cut through to the other side, where a fracture exposes it, opening a hole in the rock and creating an arch.  Initially this hole is small, but it eventually grows.  Early, the edges of the arch are sharp and blocky, like at Natural Bridge.  But, over time the edges of the bridge weather more smooth, and the arch becomes more rounded.  This is like what is seen at Delicate Arch at Arches National Monument in Utah.

Students under Natural Bridge.  Natural Bridge is sharp and blocky and is a young arch.
Delicate Arch in Utah is an old arch

Eventually, the top of the arch becomes too thin to support itself and it collapses forming pinnacles.  The pinnacles continue to weather along the layers, and form balanced rocks.  Eventually, the balanced rock will collapse, completely destroying the formations.  
Balanced Rock at Natural Bridge State Park

Sometimes, the bridges will form from a river running over the sandstone and cutting down into the fractures.  As the fracture opens, it separates a bridge from the rest of the rock, and forms a waterfall next to the bridge.  Over time, the waterfall will cut upstream, separating from the bridge.  This is the case at Rock Bridge.  The waterfall is now about 1/4 mile upstream from the bridge.
Waterfall formed by Rock Bridge

Rock Bridge with a river flowing under it

Weathering is a process of creation, but it is also a process of destruction.  The formation of the arches will continue to change until ultimately they are destroyed by the same processes that created them.

Saturday, September 9, 2017

Opals and Onyx

Tomorrow, I am releasing the limited edition

opals and onyx collection

showstopping gemstones for every occasion

Opals and onyx are two of the most popular ever-lasting gemstones in the jewelry market.  But what are they ... really?  In a previous post on August 20, I talked about flint and chert.  Today, you will discover that opal, onyx, chert, flint, chalcedony ... they are all essentially variations on the same thing - microcrystalline grains of silica.

Onyx is a banded variety of chalcedony.  The bands are created by alternating layers of microcrystalline quartz and moganite, which is essentially quartz with a different crystal structure.  Sardonyx is a variety of onyx with bands of quartz and sard, another variety of chalcedony.  (Gemstone manufactures seem to try to make their products stand out by giving different names to essentially the same minerals).  Utah blue and orange sardonyx are examples.
Utah Sardonyx collected near Nephi, Utah

Calcite onyx is actually not onyx at all.  Calcite onyx, or cave onyx, is banded layers of calcite that form from cave formations such as stalagtites and stalagmites.  It forms much the same way, with one little layer at a time slowly precipitated.  But it is calcite instead of quartz.  Honey onyx and the most popular flowering tube onyx are examples.
Flowering Tube Onyx collected near Nephi, Utah

Cave Formations at Ruby Falls, Tennesee
Opal is the least like all the other minerals - onyx, chert, flint, and chalcedony.  It is still silica, but in opal, the silica does not form crystals of quartz.  It is a hydrated, amorphous silica "ooze".  Most often, opal is associated with volcanic activity.  Silica-rich fluids from magma flow into the surrounding rock, where the opal is precipitated in pockets and layers in the rock.  The internal structure of the silica ooze makes it refract light, which gives opals their most-sought after feature - sparkle.

There are two types of opal - common opal and precious opal.  I personally feel these names do not do them justice because "common" opal is just as amazing as precious opal.  Precious opal tends to show a play of colors and multi-color sparkle and shimmer that dances in the light.  Common opal tends to be translucent and often a single solid color, or bands of colors.

Examples of common opal include Utah bacon opal and Peruvian pink and blue opal.
Utah Bacon Opal collected near Milford, Utah

Examples of precious opal include the Honduran black matrix opal and koroit boulder opal.

Honduran Black Matrix Opal

All of these stones make beautiful cabs and stunning jewelry perfect for that special occasion or to make every day feel special.

Cabochon from Bacon Opal
Cabochon from Koroit Boulder Opal

Find the Opal and Onyx Collection at  Don't forget, join Club Ruby for an instant 20% discount!

Dr. Janet Bertog, owner Ruby Mountain5 Rocks

Monday, September 4, 2017

Hurricane Harvey

Most people are fully aware of the impact that hurricane Harvey has had on Houston and the surrounding areas.  This was the first hurricane to make landfall in the United States since 2005, and it is easy to forget about the devastation these things can cause, especially after 12 years of feeling "safe".  When it made landfall, it was a category 4 hurricane, with sustained winds of 130 mph.  This was the beginning of days of torment.  Hurricane Harvey was in no hurry to leave Texas, and stalled for two days just inland, with continued heavy rainfall.

In reality, although the devastation is enoromous, the people were "lucky".  There were 60 confirmed deaths, in comparison to approximately 1500 (as many as 1800) deaths from Hurricane Katrina in 2005.  Nevertheless, Hurricane Harvey was catastrophic.

And now, only days after the remnants of Hurricane Harvey made its way across the eastern United States, we are poised for another hurricane, Hurricane Irma is headed toward the Carribean and is expected to impact the east coast next week.

While people are picking up the pieces from this hurricane and trying to put their lives back together, some people lost very important members of their families.  While rescuers were able to evacuate many people, they could not take pets with them.  Pets all over the region are abandoned, lost, confused and scared.  Rescue agencies all over the country have mobilized to help get these pets back to their families.

In Ohio, where I live, Silver Linings of Ohio is teaming up with other rescue agencies in Ohio to bring pets that were in rescues and shelters in Houston to Ohio for foster and adoption.  Meanwhile, Best Friends Animal Society is working to house the lost pets and help them find their families again.  I am sure there are agencies in your state doing the same things.

During this time, I will be donating 15% of my sales to Silver Linings of Ohio to help them bring the animals to Ohio, house, feed, and medicate them, and help them find loving homes.

Helping shelter pets in the wake of Hurricane Harvey

Janet Bertog,

My assistants ... Reddie and Angus (my senior rescue dogs)

Monday, August 28, 2017

Thomas Mountains of Utah - Volcanic Fields for Hundreds of Miles

Thomas Mountains, Utah

This summer when I did my dinosaur expedition to Utah, we took some time to go to the Thomas Mountains in eastern Utah.  We actually went there last year as well.  This place is amazing!  The geology of the region is very complex, with multiple events occurring in the same place over a span of hundreds of millions of years.  The Thomas Mountains are a volcanic mountain range that formed about 50 million years ago to as recently as 1 million years ago, near the time of the end of the formation of the Rocky Mountains.  Numerous volcanoes litter the region and most of them are calderas, giant volcanoes that erupted very violently.  Because of the volcanic activity in this area, gemstones are very common throughout the region. 

Probably the best known caldera is Topaz Mountain, appropriately named because natural amber-colored topaz is found here, along with red beryl, amethyst, garnet, bixbyite, opal and hematite.  The minerals are found in cavities in the rhyolite ash that was deposited when the volcano erupted.  It can be a lot of work to break open the rhyolite to find the cavities with the precious minerals inside.    In the picture, you can see the crater of the caldera.  The area of Eureka is also famous for many metal deposits, including gold and silver.
Topaz Mountain near Eureka, Utah

To the southeast of Topaz Mountain, near the town of Nephi, precious calcite onyx can be found.  The popular flowering tube onyx is from this area as well as yellow, red and white banded sardonyx, which will be available on Ruby Mountain5 Rocks soon.  The onyx forms when geothermal fluids from the volcanoes flowed through calcium-rich rocks in the mountains, depositing bands of colorful silica.

Flowering Tube Onyx
Available at Clidastes Stones

To the west of Eureka is the town of Birdseye, where birdseye rhyolite is found (Utah Birdseye Rhyolite will soon be available at Ruby Mountain5 Rocks, currently you can find Mexican Birds Eye Rhyolite)
Birdseye Rhyolite, Utah
Available at Clidastes Stones

South of Delta is another kind of volcano, Sunstone Knoll is a locality that is andesite lava.  In the cavities in the andesite, you can find small yellow sunstone crystals.  Sunstone is a gem variety of the mineral feldspar, the same class of minerals that includes moonstone and labradorite.

Sunstone knoll is a cinder cone.  Cinder cones are smaller volcanoes that are less explosive and produce more lava than ash.

Sunstone Knoll.  Image from

Sunstones collected from Sunstone Knoll

My most favorite gemstone from this area is the bacon opal.  Bacon opal is formed when geothermal fluids flow through rhyolite layers and deposit colorful bands of silica rich in iron minerals.  Every piece of this material is unique.  You can find specimens of bacon opal at Ruby Mountain5 Rocks, Bacon Opal.

One of the most famous and sought after gemstones from Thomas Mountains is Tiffany Stone.  Tiffany stone is becoming very rare because the locality has not been open to collecting for quite a long time and the only stock available was collected over 30 years ago.  Tiffany stone is opalized beryllium-rich fluorite and bertrandite.  This stone has a cracked marbling of creamy white and purple.  You can get your own Tiffany Stone at Ruby Mountain5 Rocks.


Utah is riddled with collecting localities for rock hounds of all types.  Some localities can be found here and here.

By Dr. Janet Bertog, Professor of Geology
Owner of Ruby Mountain5Rocks
Owner of Clidastes Stones

Sunday, August 20, 2017

Chert, Flint, Jasper, Agate, Opal .... all so popular, and yet, what's the difference??

Chert, flint, jasper, agate - these are all common semi-precious and precious gemstones found in the lapidary world.  They are all different, they all look different, and yet, they are all the same.  All of these gemstones are made of micro-crystalline or non-crystalline silica grains, similar to quartz.  So, why so many different names for essentially the same material?  Well, it gets even more complicated than that because there are many types of jasper, many types of agate... you get the idea.  

So, to start, what makes them all similar?  Rocks are generally made up of minerals.  Minerals are crystals with an orderly arrangement of atoms.  Some rocks are not made up of minerals.  For example, coal is made up of plant material, which is not a mineral.  No minerals are organic.  Chert, flint, jasper and agate are all made up of micro-crystalline, poly-crystalline quartz, a mineral composed of silica and oxygen.

Chert and flint are the most similar.  They really are essentially the same thing.  Chert is the variety that most often forms in nodules in limestone.  The formation of chert in limestone is thought to be a result of sponges (the marine animals).  Sponges make their shells out of tiny spicules of silica.  When they die, this silica absorbs into the water.  Most other animals in the shallow marine environment, including corals and clams, use calcite to make their shells.  The calcite gets recrystallized into limestone.  The silica from the sponges globs together and forms nodules in the limestone.  If you work in limestone, or in caves, this is often called "trash rock" because it is not the main rock that makes the limestone.  Chert is also found in banded iron formations, which are layers of the iron mineral hematite and chert.  Banded iron formations formed during the Precambrian, more than 500 million years ago.  It is thought that the alternating bands of hematite and chert represent seasonal changes.  During the dry season, chert crystallized out of the water and precipitated to the bottom of the oceans.  Sponges are some of the oldest animals on Earth and it is possible that this chert is remnants of these sponges, which were living in the ocean when no calcite-forming animals were around.  Up on land, things were much different.  There were no plants or animals on land during this time, the land was barren and weathering.  During rainy seasons, iron-rich weathered rock would get washed into the ocean as hematite-rich sands, depositing a layer.  This would alternate each season, with a layer of chert then a layer of hematite.  After the Precambrian, with the onset of the Cambrian, there was an explosion of new life, particularly, this was the first occurrence of animals with hard parts, shells made of calcite.  This put an end to banded iron formations.

So, long story short, chert is generally made from tiny pieces of sponge.  So what about flint?  Well, flint is exactly the same thing as chert, but it is usually restricted to the variety found in chalk or marl (marl is chalk with mud in it, chalk is very fine grained limestone - so many subtle variations!).  Some famous flint includes the Flint Hills in Kansas and the Ohio Flint Ridge.

So, what about jasper and agate?  These are also varieties of micro-crystalline,crypto-crystalline quartz, but they form by the replacement of other minerals with the quartz.  The main difference between jasper and agate is that agate is banded and jasper is not.  Jasper will replace grains of minerals in rock very slowly over time.  Petrified wood is a variety of jasper where the wood grains have been completely replaced with silica, or petrified.   There are many other types of jasper as well.  One of the neat things about jasper is that the replacement process usually creates great color patterns in the rock, such as seen in Owyhee Picture Jasper.  You will find that many of these jaspers are very similar!  That is a topic for another post.  Some rocks are mistakenly called jasper.  One example of this is Rainforest Jasper, which is really rhyolite, a type of volcanic ash.

Picture jasper with antiqued copper tree of life
Owyhee Picture Jasper
Owyhee Picture Jasper Slab
Brecciated Rhyolite (Jasper)
Birdseye Rhyolite (Jasper) Cab

Agate is generally banded and forms as the grains of quartz crystallize out around a rim or precipitate out in cavities.  Crazy lace agate is an example of an agate that forms in cavities and creates nodules that have to be cut open to reveal their beauty.  Moss agate forms from the crystallization of minerals in a mossy pattern within a background mineral.  Again, some rocks are misnamed, like Turitella Agate, which is actually not Turitella and is really a jasper.

Moss Agate Pendant at Clidastes Stones
Montana Agate
Montana Moss Agate

Turitella Agate

Some examples of jasper include Bigg's Picture JasperDeschutes Picture JasperFantasy JasperKambaba JasperLeopardskin JasperMary Ellen JasperOcean JasperOwyhee Picture Jasper.

Some examples of agate include Black Plume/Medicine Bow Agate, Montana Moss Agate, and many more!

By Dr. Janet Bertog, Professor of Geology, Northern Kentucky University
Owner of Ruby Mountain5 Rocks lapidary material
Owner of Clidastes Stones, specializing in unique and rare gemstone jewelry and home decor