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Turquoise Glossary

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Ready to head for the hills with your pickaxe and pail? Here are some terms and definitions you might need to know about turquoise and mining.

Let’s start with the obvious. If you look up the precious gemstone in a dictionary, you might find a definition like this:

 

Turquoise

[tur-koiz, -kwoiz]

 

 

 

 

 

 

 

An opaque mineral, a basic hydrous copper aluminum phosphate often containing a small amount of iron, sky-blue or greenish-blue in color, cut cabochon as a gem.

 

Here’s how it forms:

Turquoise comes into being over millions of years, as water seeps through rock containing copper, aluminum, and other minerals. The water gains color and eventually hardens. The bluer the color, the more copper is present. The greener the color, the more iron is present. 

 

Backing

An epoxy mixture applied to the back or bottom of the stone cabochon. The hardened backing keeps the stone intact during setting.

 

Bezel

 

 

 

 

 

 

 

The rounded edge of a cabochon created by using a 100-grit cutting wheel. A bezel can also refer to a strip of metal that surrounds a stone set in the jewelry.

 

Cabochon

 

 

 

 

 

 

 

Often called “cabs” for short. Rough stone cut into convex shapes without facets. They’re cut in sizes and shapes that work best for jewelry design. They may be cut to a specific shape and size, or left freeform. A backing is often used to strengthen the stone (see backing).

 

Carat

A carat is the standard weight measurement for gemstones.

 

Chert

Chert is a hard, fine-grained sedimentary rock made of quartz crystals (microcrystalline quartz). Turquoise is sometimes surrounded by some form of chert.

 

Claim-Jumper

 

 

 

 

 

 

 

Someone who illegally mines another’s claim, though they don’t have rights to it.

 

Dead Ground

This is any layer of rock that doesn’t contain turquoise deposits. Miners must blast off the dead ground in order to expose and reach the high-grade turquoise.

 

Exposed Surface Float

 

 

 

 

 

 

 

Loose chunks of turquoise rock, lying on the ground. They’re not connected to a larger formation, so they’re easily moved—by people, animals, weather. Because of that, it’s hard to determine if there’s a larger source of turquoise at that location.

 

Facet

Many gemstones such as diamonds and emeralds feature facets, several flat, polished surfaces cut at angles on the stone. Turquoise is not facetted in its finished form.

 

Freeform

When creating the cabochon, the stone is left in its natural shape. They are called “freeform cabs.”

 

Host Rock

 

 

 

 

 

 

 

The host rock is the stone that holds the gemstone or minerals. You’ll see the “host” in a turquoise cab in the matrix. (See matrix)

 

Mohs Scale

The highest-quality turquoise isn’t easily crumbled or shattered. It’s as hard as, well, a rock. The harder the turquoise, the easier it is to work with, and the more valuable it is in the market. The Mohs Scale measures the stone’s hardness.

 

Lead of Turquoise

 

 

 

 

 

 

 

Finding turquoise is labor intensive right from the start, taking hours upon hours just walking the desert looking for formations that might carry the stone. It takes a good eye and years of experience—not to mention endurance and physical fitness!

 

Matrix

 

 

 

 

 

 

 

The pattern of host rock or other natural materials visible in a cab or rough, mined turquoise. The colors and patterns vary and help buyers and jewelers determine the type of turquoise and its worth. Certain patterns, combined with colors are rare and increase the value of the stone exponentially. Some matrix examples are: spiderweb, calico, and micro web.

 

Paint

 

 

 

 

 

 

 

When searching for turquoise, miners look for “paint,” the flow of turquoise in the ground. It appears as if an artist painted a thin line with blue paint on the rocks. This gives a good indication the prospectors will find turquoise underground.

 

Tongue Test

Miners lick the stone. Yes, lick, like ice cream in a cone! Only this is to determine if the turquoise is of high grade, and the color is correct. If the stone absorbs the moisture from the tongue and the tongue sticks to the rock, the stone is not useable. If it feels like licking a piece of glass, it is a strong, quality rock.

 

Variscite

 

 

 

 

 

 

 

This mineral is a rare hydrated aluminum phosphate. Variscite ranges in color from yellow-green to light blue-green. Lacking the copper element contained in turquoise, it does not form a true, deep-blue color, but there is a degree of overlap, so one stone could be confused for the other. Like turquoise, variscite is cut into cabochons, and used in jewelry. Because the mineral is rare, jewelry bearing variscite stones were not widely available to the buying public, but still the price has always been relatively inexpensive. That’s changed. Recently, variscite has surged in demand, value and price.

 

Vein

 

 

 

 

 

 

 

A thin line of turquoise seen within the host rock.

 

White Buffalo

 

 

 

 

 

 

 

This stone is found in veins, is as hard as traditional blue turquoise, and can be cut into cabochons. It’s usually surrounded by black and brown chert, and features a fine black or brown-black spiderweb matrix. White Buffalo is formed from calcite and iron, but no copper, which would give it a blue hue. There’s just one place to find this rare stone—in Tonopah, Nevada, mined by the Ottesons.

 

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