Amazonite is a turquoise-colored gemstone.
My first encounter with amazonite was in a desert rock shop in Arizona. My husband, my vigilant rock hound and specimen scout, held up a handful of pretty blue-green stones. “How do you like these?” I liked them a lot and knew that they would work nicely in a wire-wrap necklace design. “I’ll take these turquoise stones.” I told the friendly rock shop sales lady of my buying intentions, but she corrected me. “They’re not turquoise, they’re amazonite,” she said that in a way that sounded more like ‘amazing, right?’.
So, questions facing me squarely centered on how to pronounce the newly discovered stone: More like “amazing,” which is what those stones were? Or more like “Amazon,” the big South American river and big online sales outfit? Also, which syllable in amazonite is to be stressed? The rock shop sales lady and I had different answers and orthogonal opinions about those pronunciation matters. I’ll leave you to wonder how it worked out.
What also needed working out was the difference between amazonite and turquoise. The two have a similar color, but that’s where the similarity stops. What follows are ways to tell them apart.
Amazonite is turquoise-colored stone in a white matrix. Turquoise is turquoise-colored stone in a black matrix. The background to the turquoise color is the distinguishing visual clue. It’s distinctive, if you pay attention to what did not attract you to the stone in the first place. So, don’t be snookered by the attractive turquoise color. The background is key for telling one from the other.
Elementary, my dear!
Now, here’s where a little knowledge of chemistry goes a long way. The chemical formula for amazonite is too long to fit on this line. It’s a silicate, that is, its chemical foundation is silicon and oxygen, with atoms of potassium, aluminum, sodium, and calcium in the molecule too. Suffice it to say simply that amazonite is a feldspar. Feldspars form from the crystallization of magma in veins and constitute 60% of rock in the earth’s crust. So, feldspar, of which amazonite is a turquoise-colored member, is quite a common mineral.
Turquoise also has a chemical formula that barely fits on this line. Simply stated, turquoise is a hydrous phosphate of copper and aluminum. Simply stated, its not a silicate like amazonite is. Simply stated, it doesn’t have the potassium, sodium, and calcium atoms that amazonite has in its molecule. Simply stated, turquoise isn’t even close, elementally, to amazonite.
Uncommonly common color
It’s the turquoise color of turquoise and amazonite that’s so similar. Copper is what accounts for the color in turquoise. In amazonite, the color story isn’t nearly so clear. It was believed that copper caused the turquoise color in amazonite too. But our preceding chemistry lesson–and somebody else’s elemental analysis–showed that copper is not one of the elements present in amazonite. So, where does the color come from?
The short answer is nobody knows for sure. Hoffmeister and Rossman postulated in 1985 that lead, in small quantities with water in the feldspar, cause the turquoise color in amazonite. A better answer does not appear forthcoming.
I’m not sure gemstone lovers and jewelry makers are interested enough to find out, as they appreciate amazonite for the lovely color it displays, whatever its source. And now that we know how to recognize amazonite visually, we no longer are fooled by the pretty turquoise look-alike.
In gemstone jewelry, it’s all about the color and how the gemstone appeals to one’s sense of beauty and harmonious design. In the rock shop, “Ring up those amazing turquoise-colored stones, whatever they are!”
Sources: personal experience, www.en.wikipedia.org/wiki/Amazonite , Hoffmeister, Rossman, Am. Min. 70, 794-804 (1985).