Mineral Mondays #7: Turquoise Plus Win This Turquoise Rough

Turquoise

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Turquoise is a hydrated phosphate of copper and aluminum. It is formed when water percolates through cracks in rocks that contain aluminum and copper. Over thousands of years the minerals build up filling the cracks or forming nuggets in vugs (cavities).

I think of it as the Native American gem, but it has been found and used around the world in jewelry for thousands of years. In fact, Turquoise comes from the French word Turquois which means Turkish. It's one of the minerals I unfortunately haven't been able to dig in the field. Almost all turquoise bearing sites are claimed or closed to mining. So I have to mine the mine owners and dealers for material, like the piece shown below from the Royston Mining District in Tonopah, Nevada. Oh, by the way, I'm giving that piece away to one lucky reader in the U.S. so read on.

While turquoise is found all over the world, I'm going to focus on the desert South West in The Untied States. California, Nevada, Arizona and New Mexico all produce variations of turquoise, from the light blue Californian turquoise to the multiple colored Nevada turquoise to the robin blue Arizonan turquoise to the green turquoise of New Mexico. Some of the best quality turquoise comes from Arizona. It's a robin blue color and is found around Globe, Az. similar to below, but much more vibrant. 

Botryoidal nugget

While Arizona produces some of the best quality turquoise, other areas produce highly sought after characteristics like spiderweb turquoise(sorry I don't have photos) or Royston turquoise because of it's hard matrix. There are many variables that affect the value of turquoise from it's color, pattern, hardness, locality (mine), etc. Here is an example of a turquoise cabochon with a small, pyrite inclusion which is another characteristic that would add to it's value.

Some facts about turquoise:

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• Topaz is a phosphate mineral 
• Shape - crystal - triclinic, specimen botryoidal (grape cluster looking)
• Composition - phosphate, copper, aluminum 
• Hardness - 5-6 (medium, diamond is 10) 
• Refractive index (fire) - 1.61 (diamond is 2.417 - 2.419)
• December birthstone
• Colors - Turquoise, Blue, Green, White, Yellow & Brown
• Localities - All over the world, too many to list, but Southwestern States in the US.

When purchasing turquoise you must be careful to know, where it's from, if it's been "stabilized" (hardened with resin) or if it's been colored. Those are 3 major factors to beware of. Usually if you know where the turquoise is coming from you can tell the quality of it. A lot of fake turquoise comes from China. It is actually howlite, which is a white mineral that looks like turquoise, and is dyed blue and sold as turquoise, so beware.

Before we get to the giveaway I want to show a few more pictures of turquoise

Turquoise nuggets

The Giveaway

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It's easy, just guess the weight of this rough piece from the Royston Mining District in Nevada. The first person to guess right wins it! ONLY 1 GUESS per person. ALSO, IMPORTANT! I CAN ONLY SHIP TO THE CONTINENTAL UNITED STATES. IT WOULD COST $$$ TO SHIP OUTSIDE OF THE US.

Next Mineral Mondays #8: Agate And Another Giveaway

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Thanks for reading!

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