| Turquoise is hydrous copper aluminum phosphate, CuAl6[(OH)2/PO4]4 4H2O (Schumann, 1997, p. 170). It varies in color from a sky blue to blue-green or apple-green, and is frequently fashioned with the matrix rock and interspersed vein rock. The veined material is called "spiderweb" turquoise. The blue color changes to green with high heat (of soldering) and exposure to light, perspiration, oils, cosmetics, household detergents (always remove turquoise rings before washing hands or dishes). It has a hardness of 5-6, cleavage, and a conchoidal fracture. The specific gravity is 2.31-2.84 and it is in the triclinic crystal system, crystals are rare. It has a waxy luster and both the fluorescence and pleochroism is weak.
Lapidary Journal has a step-by-step on cutting and fashioning a freeform cabochon of turquoise. The Turquoise Mystic by Tom and Kay Benham can be viewed at www.lapidaryjournal.com/stepbystep/jun03turq.cfm. |
 Image taken from Jewelry Central. |
 Image taken from The Image. |
Turquoise is opaque and has one of the highest values among opaque gemstones, second to highest quality jade and lapis (The Image). It is a treasured gemstone, used for beads by Egyptians as early as 5500 B.C., and inlaid in gold by Sumerians and Egyptians for jewelry such as necklaces, bracelets, earrings, and headdresses. It has been popular in the Orient and with South and North American Indians. For more history and lore, visit CW Jewelers. Also read the article, Turquoise is Back in Style by Sharon Goldman Edry, http://www.gem.net/style/turquoise.htm, and it is not just for hippies! Finally, another article worth viewing is at www.rockhounds.com/rockgem/articles/turquoise.html, Turquoise Blue Sky...Blue Stone by Bob Jones, Senior Editor of Rock and Gem magazine. |
| The oldest turquoise source is in Sinai, Egypt, where the mines were worked for thousands of years and believed to be worked out by 4000 B.C. although it some was rediscovered in the mid-nineteenth century and worked on and off until the 1900s. Mines in Iran were known for good quality nodules and vein material in the sky blue color. Turquoise is also found in Afghanistan, Argentina, Australia, Brazil, China, Israel, Mexico, and the US, primarily New Mexico, Nevada, Arizona (but also Texas, Colorado, and California). |  Image taken from The Image. |
 Photo date 3/02, © S.W. Aber. |
The pure blue color is rare and often turquoise is intergrown with malachite or chrysocolla, along with the host rock matrix. In the US, the aluminum (Al) in turquoise is partially replaced by iron (Fe) and thus, strictly speaking, the mineral chalcosiderite, not turquoise (Schumann, 1997, p. 170). Turquoise is a secondary mineral formed in the alteration zone of hydrothermal replacement deposits, often associated with copper deposits in arid, desert environments. An article that provides a general overview is found online as a feature article in May 2003 at www.lapidaryjournal.com/feature/may03str.cfm, Wild About Turquoise by Liz Kuhns (or enter through www.lapidaryjournal.com/feature/, Feature Article Index). |  Image taken from The Image. |
 Dyed howlite. Photo date 10/99, © S.W. Aber. |
Turquoise is porous and therefore treated by soaking in a vat of artificial resin or plastic-polymer, which also hardens and stablizes the surface. The color is enhanced with oils, or paraffin, aniline colors, copper salts, etc. Turquoise is reconstituted when the mineral is crushed into a powder, soaked or baked with a adhesive mixture; finally, this solid material is pressed and sold in blocks that are easier to cut and fashion than stabilized material. All of these enhancements reduce the value of the gem and should be disclosed at the time of a sale. Additionally, synthetic turquoise has been on the market since 1970, and imitations of turquoise have been around for thousands of years. Early imitations were made from glass and porcelain, while later imitations are various plastics or dyed howlite. Read about various treatments at www.turquoiserough.com/treatments.shtml, Turquoise Rough, A ColorWright Web Store, and follow their internal links showing images of specimens treated and natural. |
Turquoise is December's birthstone and reserved for the 11th year anniversary. It is set in both gold and silver, often with red and pink coral, as well as mother of pearl, malachite, lapis, and sugilite. The Native American Jewelry or "Indian style" silver jewelry is relatively new, that is unknown prior to 1880 (Jewelry Central or Image or where?). A trader persuaded an Indian artist to make the turquoise and coin silver jewelry, in addition to the more traditional solid turquoise beads, carvings, and inlaid mosaics. Learn more about turquoise by visiting:
| Image taken from Jewelry Central. |
Return to the Syllabus or choose another gemstone below.
| Alexan drite | Amber | Amethyst | Chalcedony | Diamond | Emerald |
| Garnet | Jade | Malachite | Opal | Pearl | Peridot |
| Ruby | Sapphire | Tanzanite | Topaz | Tourmaline | Turquoise |
This page originates from the Earth Science department for the use and benefit of students enrolled at Emporia State University. For more information contact the course instructor, S. W. Aber, e-mail: saber@emporia.edu Thanks for visiting! Webpage created: November 15, 2000; last update: January 7, 2007.
Copyright 1999-2007 Susan Ward Aber. All rights reserved.