Turquoise has been valued as a gemstone for thousands of years. It was well known to Ancient Egyptians, the Aztecs and Native Americans, and even the Chinese of the Shang Dynasty. The name turquoise comes from a French word meaning “Turkish stone, ” as the gem first came to Europe from trade routes that ran through Turkey.
Known mainly for its blue-to-green color, turquoise is a normally opaque mineral comprised mostly of copper and aluminum, with various trace minerals. Considered sacred by many Native Americans, turquoise was once mined extensively in the southwest deserts of North America. Today, more than 75 percent of the gem quality turquoise available is mined in China.
Turquoise can vary widely in color and texture, and show the presence or absence of matrix. Many factors can affect the value of an individual piece or turquoise. Some are subjective, and some have changed over the years depending on the whims of fashion. But like many colored gemstones, the color of turquoise is the primary factor in determining its value. In addition to color, the clarity, texture, hardness of the stone (as well as the presence and quality of matrix) are also factors that will affect value.
How to Evaluate Turquoise Color
Curiously, turquoise is the only gemstone that has a color named after it, yet it occurs in more than one color. The color named for the stone is the classic “robin’s egg” blue, but turquoise can occur in colors that range from white to a powder blue, to blue-green, yellowish-green, and even avocado and lime green, depending on the presence of trace elements.
Trace amounts of copper contribute to the blue coloring; chromium and vanadium add green; and iron results in a yellowish stone. Typically, an intense, medium blue is the most favored, and therefore most valuable color. In the finest quality turquoise, the color is even, with deep saturation and no matrix included.
Sometimes referred to as “Persian grade,” turquoise of this color and quality is still mined in Iran, though some deposits in the desert southwest of the United States have historically yielded this color as well. More commonly, turquoise occurs in light to medium blue or greenish blue, and can be mottled or have darker, uneven areas.
How to Evaluate Turquoise Clarity
Turquoise is almost always opaque, but can be semi-translucent at times. One notable exception is the material that is mined in Lynch Station, Virginia, which can occur as translucent to transparent crystals. Though quite small at an average of about 1 mm, translucent crystals of this type are highly valued by collectors. Turquoise can be mottled, with dark splotches, and it can vary in luster from waxy to matte to a subvitreous (or glassy) appearance.
The most important clarity factor in turquoise is the presence of varying degrees of matrix, which can greatly affect the stone’s value. So-called “spider web” turquoise has fine seems of matrix running through it, offering a dark contrast to the stone’s color. When they occur in thin, discreet lines, these web like patterns (also called “cobweb turquoise matrix”) can add to the value of the stone.
How to Evaluate Turquoise Cut
The cut of rough turquoise has little to do with the stone’s overall value, though turquoise is most typically fashioned as a cabochon. The rounded dome shape of the cabochon cut helps highlight the stone’s color, as well as its texture and matrix. The most preferred texture for turquoise is perfectly smooth, with a high polish. For necklaces, artisans can fashion turquoise into beads, or the rough material is sometimes tumbled into “nuggets.” Turquoise can also be engraved or inlaid with gold, or used as inlay for jewelry and other pieces.
How to Evaluate Turquoise Treatments
Because there is very little naturally “hard” gem quality turquoise available, all but the highest quality turquoise is likely to have been treated in some way. Some treatments are to stabilize stones that might be subject to fracture or fading, and other treatments can enhance appearance.
For centuries, oils and waxes have been applied to help a stone’s polished sheen, but modern hardening techniques have been developed to prevent breakage, especially for stones that are drilled for strung beads or tumbled for polishing.
This kind of stabilization is common and will permanently harden the stone and keep it from absorbing skin oils and other natural elements that fade the stone’s natural color. These techniques can also include the addition of dyed resins to enhance the color of lower quality turquoise, and should always be disclosed by reputable jewelers.
How to Sell Your Expensive Turquoise Jewelry
Contact Diamond Estate Jewelry Buyers today for a free verbal appraisal of your turquoise ring, earrings, necklace, or loose turquoise gemstone. You can also get the process started online by telling us about the turquoise jewelry you wish to sell in the contact form below.
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For more information about selling your turquoise, read our article: How to Sell Turquoise Jewelry.