Turquoise: What to Know Before You Buy

Think you know turquoise when you see it? It seems straightforward: the blue gemstone is familiar to most of us. Unfortunately, this is a frequently faked gem. Dig deeper and you'll learn that place of origin, mineralogical factors and man-made alterations all come into play when determining value and quality. Know before you buy.

Why are there different types of turquoise? Simply said, because it can be made up of different materials. Turquoise isn't a primary mineral. This means it develops as a result of geological forces on other existing minerals. It always forms in desert regions and always in the presence of copper. The weathering action of groundwater together with copper, phosphate and aluminum over time forms the gemstone.

Sometimes brown or black veins or traces of the mother stone run through turquoise. This is called matrix and it can look like a spider web. Chunks of pyrite or fool's gold might be included, too. If there is no visible matrix and the turquoise is pure, intense robin's egg blue, it's considered the finest turquoise. For thousands of years, Persia, or Iran as it's known today, was the source of the most valuable turquoise. It is Iran's national stone.

In other locales, iron substitutes for the aluminum to varying extents and turquoise takes on a greener color. Depending upon the place of origin and the mineral composition, turquoise can be powder blue, green, whitish, or yellowish blue.

In Israel, a beautiful mixture of turquoise with malachite and chrysocolla called Solomon's Stone, or Eilat stone is popular. This is Israel's national stone.

Turquoise is abundant in the American Southwest desert. Native Americans used it for centuries and as copper mining grew, more turquoise deposits were found with the copper. Often the turquoise was simply dumped as a waste product of the mining process. Arizona, Colorado, California, New Mexico and Nevada all have deposits.

In Bisbee, Arizona, turquoise in shades of blue and some greens came out of a copper mining operation. One deep blue, high quality shade became known as Bisbee Blue. Although it's no longer mined, Bisbee Blue stones are still on the market.

Another valuable American source is Sleeping Beauty Mountain in Globe, Arizona. Sleeping Beauty turquoise varies from light sky blue to royal blue, and doesn't show a matrix. Sleeping Beauty Pit is actively producing today and this fine turquoise commands top prices.

For all its beauty, turquoise has some traits that enter into any discussion of quality and price. It's a relatively soft stone. Minerals are rated on a hardness scale known as the Moh's scale, and range from diamonds, the hardest, at ten, down to talc, the softest, at one. Turquoise rates at six, which is about the same as window glass. It is also porous, and will absorb body oils.

Because of its softness and porosity, turquoise is vulnerable to damage. Since ancient times, jewelers protected it with a coating of wax or oil. The natural surface texture is somewhat waxy, so this is a widely accepted practice.

Lots of lower-grade gemstone material used to be discarded, until the idea of stabilizing treatments came along. Epoxy and resin can be impregnated under pressure. This is labeled stabilized or bonded turquoise. The Federal Trade Commission requires that all gem sellers properly label stones that have undergone any adulteration process. Stabilized stones are fine as long as they are honestly labeled, and should sell in the medium price range.

Turquoise easily absorbs dye, so naturally pale stones can be enhanced to look darker or more intense. This is low quality material. Lowest of all is reconstituted or reconstructed turquoise, which is bits and pieces mixed with epoxy; think chicken nuggets.

Lots of outright fakes are on the market, too. Howlite, a white stone with matrix lines, is frequently dyed turquoise color.

To add to the confusion, a gem labeled "yellow turquoise" is really not related at all, but is a blend of serpentine and jasper. Since yellow tones sometimes occur in the real thing, this is doubly confusing. Merchants use quotation marks around the term to indicate that it's faux.

Chalk turquoise popped up recently in the market. This is a soft, chalky material found near turquoise deposits. It is dyed apple green, lime green or fuchsia, and stabilized with epoxy. There's controversy about whether this should be called turquoise. It's gaining popularity and is cheap.

If you bypass the fakes and adulterated forms and invest in the real thing, be sure to properly care for your turquoise. Remember that even the finest quality gems are porous and should never be exposed to chlorinated swimming pools, prolonged intense sun and cosmetic chemicals. Don't let perfume, hair spray, lotions or sunscreen come in contact with turquoise. Clean gently with a soft cloth.