Friday, October 5, 2018

Colorful Moss and a Mossy Surprise!

As my regular readers know, I love listening to the stories the rocks tell me! If you're looking for a category of rocks that are especially chatty, you can't beat those we call "mossy". There are others that love to tell stories, including rhyolite and dendritic rocks, and they're close behind. But nothing beats the storytelling talent of a mossy rock.

You may have noticed I consider mossy rocks and dendritic ones to be different items although some people use the terms interchangeably. For details about how they differ, see my previous blog post "Thanksgiving with Dendrites."


 

I call this beauty "The Fire Swamp", because it reminds me of the scenes in the Princess Bride
movie where Westley and Buttercup fight their way through the Fire Swamp while trying to evade capture. As a bit of an aside, their major danger there was "rodents of unusual size" and now there is actually a documentary movie about huge swamp rats (nutria) infesting Louisiana titled Rodents of Unusual Size, check it out on IMDB.

TOTALLY ENCLOSED MOSS 

Like  the cab above, I've had the good fortune to work with some beautiful colorful ones from around the world, even if I don't always know where they came from. At the lapidary shop where I go every week, they'll often ask where I found a particular rock, and they're getting to expect my answer to be along the lines of "Tucson" or "the show last weekend" instead of some prospecting site. This delightful mossy agate is keeping its secrets so far, When it finally tells me what it wants to look like, I'm all in!



This cab is made from fully-enclosed moss in a clear quartz matrix and I'm pretty sure I know where it's from. This is from a slab of Regency Rose Graveyard Point Agate from the Owyhee Mountains in Oregon. This one told me it felt like fire and smoke and that's the story I tried to show when I made this cab.










This is very different kind of mossy agate. This one has a name I'd never have guessed from looking at it. It's Stinking Water Plume Agate!  That name would seem to fit better on the "Fire Swamp" at the top.  This material has a delightful snowstorm story and it hails from Stinking Water Pass in Oregon and I've only seen it available at a show once. Grab it if you see some. It makes the most beautiful winter-scene cabs!





SURPRISE!  MOSS OUTSIDE THE ROCK!

I cut this bubbly beauty off the edge of a piece of Regency Red Ghost Graveyard Plume Agate. The way this happens is the plumes actually form first and then over time they are surrounded by agate. In my experience, many pieces can be sliced and often take a wonderful polish if they are solid enough.  This one seems to be showing me a wildfire with strong winds. Or, it could just be that I live in Northern California and this has been a horrific year for wildfires. What do you see?


This whole slab is less than four inches long. I love the imaginary mouth complete with quartz crystal teeth and the red lines. The lines themselves are only about as thick as a sewing thread, and they have teeny-tiny quartz crystals coating them like a blanket.

I photographed this one wet because the red lines look so fragile and the white bits matrix are nothing more than a collection of bubble-like material, that I'm afraid this one might not make it through the polishing stage, so I'm keeping it as a specimen.



Admit it, this one looks like a snail on its way off the page! At less than three inches long, it is one I love to look at. Theoretically, I could cut off the last third to make a cab. The other side has several interesting small vugs lined with biotryoidal quartz, but I'd sure miss my snail!






Has a rock told you as story lately?  Send me a picture of the rock and the story it told you. Maybe I can use it in a future blog post.

Until next time, I'm you Lapidary Whisperer,

Donna

Wednesday, September 5, 2018

THERE'S A TIFFANY STONE - AND IT'S NOT A DIAMOND

   When I first heard of Tiffany Stone, I expected it to be a soft, cool aqua, like the Tiffany Jewelry boxes; Pantone 1837 for those of you who, like me, love side trips when you're doing research. The color number refers to the year that Tiffany & Co. was founded. That wasn't the color. It's purple!

Tiffany Stone is also the name of an actress known for her work in A Very Harold & Kumar 3D Christmas.

 

Enough trivia. Back to the important stuff, rocks!

 

YUP, ROCKS

 

A lot of what I write about in my blog is committing lapidary on minerals, but Tiffany Stone is actually a rock. Here's the difference:

MINERAL: A mineral has a specific chemical composition and you will see the chemical formula for each mineral tells what the chemicals in the mineral are and their proportions. For example, the mineral Quartz is SiO2 which tells you it is made up of Si, or silicon, and oxygen. Some varieties, like Rose Quartz, have colors as a result of inclusions, but the inclusions don't change the formula. Usually, minerals each have a distinctive crystal formation that results from the atoms of their formula. For more details on how this works, Click Here

  

ROCK: Unlike minerals that always have the same formula, rocks are formed as an aggregate that includes more than one mineral. Rocks are not identified by their chemical formula, but by the way they are formed; Igneous (formed by fire), Metamorphic (changes over time), and Sedimentary (mineral or organic bits that have settled and hardened). Tiffany Stone is a sedimentary rock that is primarily fluorite with additions including opal, calcite, quartz, and others.

BEWARE

When you see some at a show or online and it's expensive, don't be surprised. The only place it is mined in the world is at the Brush Wellman beryllium mine at Spor Mountain in western Utah. If a vendor tries to tell you it is so expensive because it is imported from China or Africa, walk away. It's expensive because it's rare.

TIFFANY STONE ON THE LAPIDARY BENCH

I purchased my specimens at the Arizona shows in the winter.  I got two nice, but not remarkable, nodules.

When I sliced the first one, I noticed it was awfully soft. Depending on your source, it will run between 4-5.5 on the Mohs scale, and even at the top hardness it is a pretty soft stone. When you make cabochons with it, plan to mount them in protected settings (not rings) because it's very easy to scratch, ruining the surface finish.

One of the distinctive aspects of Tiffany Stone is the swirling pattern often found. It became a problem for me because my piece was so soft that a bit of it flaked off where the swirl met some different-colored material on my grinder wheel. I stopped right there and stabilized all my slabs before continuing any further.

I also realized that I could skip some of my wheels because of the softness.  I have a 50,000 grit wheel which normally makes anything shine, but I found it took cerium oxide on leather to get the best possible finish which was a luster more than a shine. 

WOULD I BUY IT AGAIN?

That's the question I ask myself when I'm working with a new material. I'm afraid my answer is that I probably won't. 

On the plus side, it's easy to work on (after I stabilized it).

On the minus side, it's expensive and doesn't take a real shine. My pieces are roughly the same color as amethyst/purple sage agate which is much harder and reliably takes a high shine.

Have you worked with this material?  If so, what was your impression?

I hope you enjoy my blog post. If you have any questions, let me know and I'll do my best to answer them. All the photos in this post were taken by me. They are available for a small fee. Please do not take and use them without permission--it's stealing. Thanks for supporting ethical behavior on the Web!

See you next time!

Your Lapidary Whisperer,

Donna

         found in beryllium ore found in beryllium ore

 


 

 

 




 

 

 

 

 








Home » Gemstones »



Tiffany Stone



Author: , Ph.D., GIA Graduate Gemologist

Tiffany Stone
A Tiffany Stone nodule, sliced in half and polished. Can you see why some people call it "ice cream stone"?   Public domain image by Scott Horvath, USGS.

What Is Tiffany Stone?

"Tiffany stone" is a trade name used for a purple, blue and white gem material that can be cut and polished into beautiful beads, cabochons and tumbled stones. Geologically, Tiffany stone is a rock composed primarily of fluorite with smaller amounts of opal, calcite, dolomite, quartz, chalcedony, bertrandite and other materials. Other names used for Tiffany stone are "opalized fluorite," "ice cream stone," and "bertrandite."
Tiffany Stone
Utah Tiffany Stone: "Tiffany Stone" is an unusual material found as mineralized nodules in a beryllium tuff at the site of the Brush-Wellman beryllium mine. It is thought to be an opalized fluorite. Tiffany Stone is also known as "bertrandite" and "ice cream opal." It is a rare material found only at the Brush-Wellman location.

Where Is Tiffany Stone Found?

Tiffany stone is a rare material. It is mined at one location worldwide - the Brush Wellman beryllium mine, at Spor Mountain, western Utah. It occurs there as nodules that are part of the ore produced at the mine. The nodules typically contain between one and two percent beryllium by weight.
The United States Geological Survey reports that the nodules are carbonate clasts that have been largely replaced by fluorite. Small amounts of bertrandite, a beryllium mineral with a chemical composition of Be4Si2O7(OH)2, occurs as submicroscopic grains within the fluorite.
Almost all of the Tiffany stone mined at Spor Mountain is crushed and used to produce beryllium. A small amount has been carried out of the mine by employees, and a small amount has been gathered by collectors who have rarely been allowed into the mine. These are the only sources of the gem material because Brush Wellman has always been interested in producing beryllium and has not been interested in Tiffany stone.

Other Names for Tiffany Stone

The most appropriate name for Tiffany stone is “opal fluorite” or “opalized fluorite.” These names reasonably represent the composition of most specimens. Another popular name is “bertrandite.” That name is incorrect because bertrandite is a mineral, which only comprises a few percent of the rock known as Tiffany stone. It is also called "ice cream stone" because of its delicious color.
There are numerous stories behind the name “Tiffany Stone.” Some people attribute the name to Tiffany and Company, the famous luxury goods retailer. The company has never been associated with the mine or with Tiffany stone. Others attribute the name to the daughter of a Brush Wellman employee who collected the colorful nodules brought home by her father. This story is possible, but the names of the miner or his daughter are not found in any written record.

Where Can You Buy Tiffany Stone?

Jewelry made with Tiffany stone is unlikely to be found in a mall jewelry store. Instead, it is most likely to be sold at a gem and mineral show, at a rock shop, or by a lapidarist at a craft show. You might also find it at an online craft marketplace such as Etsy. Some of these sellers are likely to be the same person who cut the stone and made the setting. You will rarely find that when buying diamonds, emeralds, rubies or sapphires!

About Using Tiffany Stone in Jewelry

Although Tiffany Stone can be very attractive, there is an important thing to consider when using in jewelry - it has a Mohs hardness of only 5 to 5 1/2. That makes it very easy to scratch. If Tiffany Stone is used in a ring, it will quickly show signs of wear and lose its nice polish and luster. For that reason, Tiffany Stone is best used in pendants, beads, earrings and other types of jewelry that will not be subjected to abrasion.
One thing about Tiffany Stone that will probably make you happy is its price. Even though it is very rare and quite beautiful, cabochons with beautiful color, pattern and size can usually be purchased for $75 or less. It also looks great in white metal. That allows it to be placed in a sterling silver setting, getting you the whole piece for a price of $150 or less.

A

Wednesday, August 1, 2018

The Wonder From Down Under - Boulder Opal




Boulder opal has a special place in my mind.  Most of the times I've seen precious opal in jewelry, it is absolutely beautiful and obviously exceedingly special. Yet, boulder opal, which is a type of precious opal, has a striking ying/yang quality of extraordinary beauty in a matrix that is as ordinary-looking as dirt.

 

When this piece was broken, it cleaved along a plane of opal leaving a lot of it exposed, but very difficult to use. The opal itself is exceedingly thin and the surface is uneven, so it can't be cabbed.  Boulder opal is mostly cabbed by cutting across the thin lines of opal to emphasize the difference between the opal and the matrix.

 

But, when it comes to capturing every bit of the incredible color, hope springs eternal! I found a bit a little over one inch long that had opal showing along the
top edge.  There wasn't enough on any side to do a proper cabochon, but there was a little bit.  I made it into this free-form cab that looks like it is flowing through the matrix.  I didn't grind it down to make a smooth surface the whole way; partly because I didn't want to waste any of the gorgeous opal and partly because it gave more of a look like it was active and moving. 

  

OPAL FOR CRAFTSPERSONS

The natural irregularities of opal make it unsuitable for most commercial jewelry making.  Much of the material you see, especially if it is reasonably priced, is likely to be laboratory-created. From the craftsperson's point of view, it is a beautiful, predictable product to work with.This pendant I received as a gift shows two varieties of fire opal and I love it and I'm pretty sure it was made with lab-created stone.



 

WHERE IN THE WORLD?

You won't find this very cab-worthy stone nearby unless you are in Queensland, Australia although small amounts have been reportedly found in Brazil and Canada. It's a lot easier to get it the way I did--I purchased two chunks at the show in Tucson earlier this year. One of them is pictured at the top of this blog post.

 

ORIGINS

Back when dinosaurs were alive (the Cretaceous period - approximately 50-65 million years ago), silica from decomposing rocks mixed with water creating a gel. This settled into the cracks in the ironstone or sandstone boulders or puddled on the top and solidified over time become boulder opal. 

Notice I called this "precious" opal; there is also an opal material called "common". The difference is both how it formed and more importantly, how it looks.  Precious opal is formed when the gel opal sets down in a series of rows. When seen in the light, it flashes iridescent colors that  can include red, yellow, blue, green,  often called "fire" because of the dramatic play of color, sometimes called "flash". The value of the stone depends on the drama in the flash. 

 

Common opal, on the hand, is well, common; but not without its charms.  A friend once gave me a hunk of common opal. I took one look at it and decided it looked like halibut to me, so I tidied it up a bit and liked it so much I ended up making a meal display for the "Rock Hard Cafe" display I take to shows.  My halibut is shown here with a sandstone baking potato and some jade peas.

 

CARING FOR YOUR BOULDER OPAL

You've probably learned that opal dries out and has to be stabilized in water, with oil, or chemical preservatives like Opticon. 

According to Opals Down Under boulder opals are very stable, can not absorb water, and are unlikely to crack. They are about the same harness as glass (about 6.5 on the Mohs scale). Soaking a boulder opal in water may hide small flaws (be sure to see it dry if you're thinking about purchasing it), and rubbing it with oil will only make your boulder opal oily, but neither will do anything to enhance your stone.

In terms of preventing damage, Opals Down Under states, "The only major things that can damage your opal are impact, extreme fluctuations in heat (e.g. placing your opal over a flame) or exceedingly low humidity for long periods. Extreme variations in heat cause the opal to expand and contract, causing cracks or crazing." One thing that can definitely damage opals over time is having it touch other surfaces and acquire tiny scratches that affect the shine. If that happens, a professional jeweler can polish the stone and remove the scratches. The possibility of scratching these beautiful stones is why many people choose to wear their opals as pendants or earrings to protect them from contact with other surfaces.  It's also a good idea to store them in a jewelry box or bag. 

If you're thinking about working on some boulder opal, I say go for it!  The material is soft enough that it won't take forever to cut, shape, and polish it, and you'll love the results!

Have you worked with boulder opal?  I'd love to see a picture of the cabs you made!

 

Until next time,

Your Lapidary Whisperer,

 

Donna







 

 

 





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