Turquoise is one of three birthstones for the month of December (the other two December birthstones are tanzanite and blue zircon). T urquoise has been prized by cultures all over the world for over 5,000 years. Turquoise is a semi-translucent to opaque gem that ranges from blue to green and often has veins of matrix (remnants of the rock in which it formed) running through it.
Turquoise has been mined in the Nishapur district of Iran for more than 1,000 years. The prized even-colored, intense blue turquoise from this region is dubbed “robin’s egg blue,” “sky blue” and “Persian blue.” Trade professionals now use these terms to describe turquoise of this color – regardless of the source.
Although New Mexico was the largest producer of turquoise in the U.S. until the 1920s, today most of the U.S. production of this December birthstone comes from Arizona and Nevada. Mines have names like Dry Creek, Easter Blue, Emerald Valley and Fox. The Kingman mine in Arizona is a historically important source that is known for producing intense blue turquoise. Now closed to turquoise mining, Arizona’s Sleeping Beauty mine was a prolific producer for more than four decades. Today, China is the world’s largest producer of turquoise. Hubei Province, in central China, is the source of most of the gem-quality turquoise currently being mined there.
Turquoise has a Mohs hardness of 5-6. Turquoise is often treated to improve its durability, appearance and polish. Turquoise can be dyed or chemically enhanced by adding an epoxy or acrylic resin for greater hardness or better color.
Turquoise is generally stable to light, but high heat can cause discoloration and breakage. Turquoise can be damaged by acids, and it can be discolored by certain chemicals, cosmetics and even skin oils or perspiration.