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.
Tanzanite is one of the birthstones for December (the other December birthstones are turquoise and blue zircon). The tanzanite birthstone is often described as “velvety,” mostly because of its deep and saturated color, which ranges from a pure rich blue to violet. The Merelani Hills of northern Tanzania is the only place on earth where tanzanite is mined comercially. North of the mines tower the snow-covered slopes of Mount Kilimanjaro.
Most tanzanite begins as brownish zoisite that is heat treated to produce the blue to violet hues that characterize this December birthstones. The resulting color is permanent, and there are no additional durability concerns.
Tanzanite has a hardness of 6 to 7. It can abrades easily and is therefore recommended for earrings and pendants. Protect tanzanite from high temperatures and sudden temperature changes.
Zircon is one of the birthstones for December (other December birthstones are turquoise and tanzanite). Zircon gemstone colors are red, orange, yellow, brown, green and blue. Colorless zircon is known for its brilliance and flashes of multicolored light called fire. The sparkle of zircon is second only to diamond.
Zircon is often located near sapphire sources. In addition to Sri Lanka and Australia which are major producers, countries where the two gems overlap include Myanmar, Vietnam and Cambodia.
Zircon ranges from 6 to 7.5 on the Mohs scale of hardness. It is commonly heat treated to produce blue and colorless varieties, as well as orange, yellow and red. The gem is generally stable when exposed to light, but some heat-treated stones may revert to their original colors (usually light brown) after prolonged exposure to bright light. Exposure to heat can alter the color of some zircon.
Because zircon tends to abrade, it is best to avoid wearing it in rough conditions, such as while gardening, playing sports or doing dishes.
Don’t be confused by the name. Zircon is a natural, magnificent, and underrated gemstone that has been worn and treasured since ancient times. It’s not cubic zirconia.