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Is it turquoise? The birthstone for December.

Slightly bafflingly, there are three birthstones for December. Turquoise, zircon and tanzanite. A conundrum when I am trying to write about each month’s birthstones! I thought about writing about zircon and my mother asked, “Isn’t that the bad guy in Flash Gordon?” I thought about tanzanite and hit another solid wall: I get as far mentally as “It’s purple.” And my brain locks up.


Which left me with turquoise, a glorious opaque blue green mineral!


In antiquity, turquoise (which is a copper ore) came from mines in Iran and other parts of the Middle East. Today, much of the world’s turquoise comes from the western US and Mexico.


The perfect turquoise is a clear, un-muddied robin’s egg blue and has been used in jewelry, pigment for paints and inlaid into sculpture. But unfortunately, this perfect blue is rare and valuable. A softer, lighter form of turquoise known as chalk turquoise is more common and used extensively today.


Turquoise from the Sleeping Beauty Mine, Arizona

How do you know how good your turquoise is?


-Is it from a named mine in the Southwestern US? Mines like the Blue Bird, Kingman and Sleeping Beauty mines of Arizona are originally copper mines and have mostly closed over the years. (Those three at least have recently reopened to fuel the gem trade.) My picture at the top of the post is all Sleeping Beauty turquoise.


-Is it from Iran, the Sinai Peninsula or someplace known as a place that has turquoise? There are other mines than the Middle East or the Western US, but not very many.


-Does it say “Made in China”? China has many excellent gemstones and gem cutters, but is also a hotbed of fake and falsified stones.


These aren't actually turquoise....

-What color is it? As I said before, the best turquoise is robin’s egg blue. But many types, heated or slightly less pure, are blue green or even just plain bright green. It depends on the mine. (There are even some Nevada mines that produce yellow-green turquoise because of phosphate contaminations.)


-What color is it? Part 2. Turquoise comes in shades of blue and green, getting lighter in color until it is almost white. Darker colors are more valuable but beware of dyed pieces! There is no such thing as purple or red turquoise and dyeing lesser stones to look valuable is depressingly common. (Hint: many dyes will rub or wash off.)


Chalk turquoise that is both dyed and stabilized.

-How does it reflect light? This is luster. The luster of good turquoise is waxy or oily, chalk turquoise is flat, dull or powdery. If your gem is translucent or semi translucent it is not turquoise!


-How much matrix does it have? Matrix is the part of the stone that is NOT blue (usually brown or black). Many Nevada turquoise mines have beautiful blue, blue green or green turquoise that is gorgeous and valuable. Just not as valuable as the no-matrix turquoise.


Un-dyed turquoise in various colors with matrix, stabilized.

-Is it a nugget or a cut stone? This isn’t so much about value but be aware that there are many turquoise fakes out there and turquoise tends to form in veins and nodules: if your piece is too large and cut perfectly, beware!


-Has it been treated with glue or resin? Glues and resins darken the color and make chalk turquoises durable enough to work with and cut. The best turquoise has not been waxed, hardened or stabilized.


Un-dyed but stabilized chalk turquoise.

-How heavy is it? Turquoise has a specific gravity of 2.6 to 2.9. For comparison, water is 1, clay (dry) 2.6 and iron 7.2. So your turquoise should be relatively light, but NOT float in water (which is plastic).


-Does it fizz in acid? Turquoise does melt in heated, strong hydrochloric acid (not usually found in houses and NOT to be done at home!) If your gemstone reacts with acid it is not turquoise but something with the right texture like limestone or magnesite that has been dyed. (Despite not fizzing, remember that turquoise tends to be a bit porous, so try not to coat it with hand lotion, bug spray or other chemicals!)


-Is it labeled “reconstituted” or does it have “floaters”? Reconstituted turquoise is turquoise chips or powder that have been floated in resin and dyed (there is almost no real turquoise in it!).


-Is it glued to something? Good turquoise naturally forms as lumps, veins or coatings on other rocks and sometimes is too thin to be used by itself. If it is very thin it is often glued to a backing to make it stronger. Backing doesn’t reduce value, but be aware that it means your turquoise piece isn’t as large as it looks.


-How much did it cost? Fraudulent sellers will sell you high priced fakes, but reputable sellers will not be cheap – good turquoise is too expensive and rare, and the market too stable for a sudden price drop.


Good turquoise is a rare and valuable gemstone that looks equally good set in silver or gold. Jewelry from the Americas tends to pair turquoise with silver, green malachite and bright orange-red coral. It is expensive enough that I don’t normally stock it. But if you want something in turquoise, contact me! I am always happy to create a special order.

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