Gemstone Treatments
by Judy Ellis
These gems are HOT!
I'm learning so much as I get to know our line of gemstone beads - studying up on such semi-precious gemstones as seraphinite and bronzite, and trying to figure out how the Dog Teeth Amethyst earned its name.

(It has nothing to do with canine incisors, I discovered, but everything to do with the Dog Tooth Violet, a wildflower in the eastern U.S. It's evidently not actually a violet; it's more like a tulip, and it gets its name from its "dog tooth" shaped bulbs. Now, that's more than you ever wanted to know, isn't it?)
Heating Stones is just Part of the Gem Business

Most all the gemstone beads in WireJewelry's line are natural stone in their natural state, but a few - onyx and sardonyx, for instance - are described as "heated" natural stone. I started worrying about that. Could I wear my onyx earrings to the beach? And what if I accidentally left my new bead bracelet in, well, the oven?
Judy Ellis's Gemstone Treatments - , General Education, , Sardonyx Rectangle Beads
We have received questions in the past about the advisability of adding beads to metal clay items that will be cooked in a kiln.

This question led me on a discovery tour of "heated" stone. En route, I gained a new appreciation for this method which has been used since ancient times to enhance the color of stone; that is, make it deeper, darker, or clearer. First thing I learned is that the vast majority of the sapphires you see are heated; otherwise, you'd see a lot of murky blue.
Onyx, too, is a gemstone that you rarely see, well, I'll call it cold. The onyx in three of our beads - onyx, matte onyx and sardonyx - is like most onyx, in that it originated as plain agate.
Judy Ellis's Gemstone Treatments - , General Education, , Matte Onyx beads
These Beads are Cooked - Permanently

Don't worry about your bracelet falling into the oven. When gem producers say words like "heated", they don't mean "baked"; what they really mean is downright "scorched." The stones are subjected to temperatures of between 500 and 1,600 degrees Celsius in large, computer-controlled furnaces.

The goal of this heat treatment is to rearrange the structure of the atoms - often dissolving microscopic bubbles and specks to improve the clarity of the stone by eliminating cloudiness. Other times, as with a ruby, temps are high enough to nearly melt the stone, transforming the aluminum oxide into a new crystal structure and producing a brilliant red.
Rocks aren't Strangers to Heat

This heat process, we're assured, it's not anything the stone hasn't gone through before. When you think about it, heating a stone to enhance its color is merely continuing the process that began in, say, the lava flow; if left in the earth, it would continue this process on its own.

However, there does seem to be something hammy in taking millions of years and compressing it into the length of a football game.
Heating is just one of several common treatments

A couple of other stones in our bead selection have been treated. Our smoky quartz beads have been irradiated to produce their dark-brown color. This treatment is almost as common as heating the stone. The flamboyant blue and purple crazy lace agate has been dyed. The only beads that are not actual gemstones are the cherry quartz & goldstone, which are actually beautified glass
Judy Ellis's Gemstone Treatments - , General Education, , Smoky Quartz beads
Even the early Romans heat-treated stones to transform boring into brilliant, just as our modern gemologists do. That's because there would be very few colorful - yet affordable - gemstones on the market, as it's very rare for gems to naturally occur in the rainbow hues we love.

Affordable is the key word here. Robert James FGA, GG, gives this example: A rare 3-carat sapphire that comes out of the earth a brilliant blue could cost you upwards of $20,000; compare that with $1,500 for the same-sized sapphire that earned its color through heat treatment.

Some gemstones we use wouldn't even exist without heat treatment. I'm thinking particularly of citrine, which is heat-treated amethyst. And purplish-blue tanzanite begins it gem life as a dull, reddish brown.
Heated to Last

So, how will this process affect your jewelry? It won't. Heat treatments produce a permanent change, so wearing your stones even daily won't affect them. However, as with most gemstones, onyx and sardonyx should be kept away from exposure to extremes of heat and household chemicals that can damage the stone.

As for firing stone beads in a kiln - that's pretty complicated. Here is a , wonderful chart (36.2KB PDF download) though, that will give you some guidance. Interestingly, it recommends against firing any quartz, from agate to amethyst. Cubic Zirconia stones, however, will stand up to extreme heat - neat!
Know what you're Getting

To safeguard against any falsities related to colored gems, always buy your gems and beads from a reputable distributor. These dealers will most often know if a gem is heat treated, and are legally bound to pass that information along to you; however, some may not know the origins of the gem if it's imported. Most vendors are honest and forthcoming, but remember that it's your responsibility to ask.

That's one of the primary factors in Wirejewlery's decision to go with a reliable U.S. distributor for our bead line. You can trust that the bead you see on the web page is the bead you'll receive.

So, don't worry, be happy, and delight in all the bright colors you want!

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  • Category: General Education
  • Technique(s): General Education