Turquoise, formed from hydrated copper aluminum phosphate, is one of the earliest gemstones ever mined, starting 3,000 years ago in Persia (now Iran). The sky-blue stone mined there was treasured because it was believed to have healing properties and the ability to protect or warn the wearer of evil. Because of its scarcity, this beautiful blue turquoise is no longer mined in Iran, and so antique Persian turquoise jewelry, often carved and inlaid with gold, is extremely valuable. Such pieces, like necklaces and amulets, first came to Europe through Turkey, hence the name, “turquoise.” However, this microcrystalline conchoidal stone has been found all over the globe, including in the former USSR, Afghanistan, Australia, Brazil, China, Chile, Australia, Tanzania, Turkestan, England, Mexico, and the United States. Cultures throughout Asia, Africa, and the Americas have attributed spiritual powers to turquoise. The light and fragile material can range from opaque to semi-translucent, with a waxy to dull luster, and its colors, which vary based on their iron and copper content, span from China blue to deep blue, and from blue-green to yellowy green. In Tibet, green is the most valued color of turquoise. Turquoise often has “inclusions” from the mother stone or “matrix” that held the turquoise as it formed, and this creates a “spiderweb” effect of brown, black, or ochre veins. Sometimes the spiderwebbing that perforates turquoise nuggets can make them easy to break apart if not handled correctly. Turquoise mined in the U.S. and Mexico is greener and often has more inclusions than the vein-free sky-blue version treasured in Persia. Turquoise may be used for beads, cabochons, or carved pieces like cameos in necklaces, earrings, bracelets, brooches, and belt buckles. The most valuable turquoise available today comes from the Sleeping Beauty mines in Arizona; ideally, it is dark blue and matrix-free. A row of this grade of turquoise in 12mm round beads should cost as much as a row of 4.5mm faceted rubies. In the late 1800s, Navajo artisans began to incorporate turquoise mined locally into their silver jewelry, but it was quickly mined out. A trader named Lorenzo Hubble began to import cut turquoise from Persia for the Native Americans to use. Then, in the early 1900s, a new mine for cut turquoise opened in Nevada. Soon other American mines followed. By then, it was expected that Native American jewelry would include turquoise. Zuni, Hopi, Navajo, and other tribes all developed distinct turquoise styles. For example, the Navajo created what is known as the “squash blossom” necklace style, which features a crescent-shaped pendant covered with turquoise beads. This style may have come from the pomegranate motif that the Spanish conquistadors brought to Mexico, but there is little evidence the Native Americans intended this design to represent that flower. This style was also adopted by the Zuni. Zuni jewelry is known for its rows of “snake eyes,” which are small, rounded, high-domed cabochons, often made of turquoise or coral, as well as its “petit point” jewelry, a style that originated in the 1920s and is made of tiny hand-cut rounded, oval, or square turquoise clustered in unique designs. The Pueblo tribes, and particularly the San Domingo tribe, were known for their use of turquoise in mosaic jewelry, as well as their disk- or tube-shaped heishe beads. The Zuni were the first to introduce turquoise animal-shaped fetish beads. If the turquoise in such Native American pieces has a matrix in it, sometimes it is also possible to identify which U.S. mine the stone came from, but not always. In the 1950s and ’60s, several of the most glamorous jewelry collectors in the United States and Europe, such as Ava Gardner, had parures with pendent earrings, necklaces, bracelets, and brooches fashioned out of large sky-blue and matrix-free Persian turquoise beads set with small, faceted diamonds. Actress Merle Oberon wore such a parure, one from her own collection, for her role as a glamorous duchess in the 1967 movie “Hotel.” Opera singer Renata Tebaldi wore a costume jewelry piece for her lead role in “Adriana Lecouvreur” in Spain. Later, she had the set upgraded with real diamonds and turquoise. Countess Mona Bismarck had two particularly exquisite floral-themed turquoise-bead necklaces, one with a résille net setting and another made with twisted gold wire. In the ’70s, Native American jewelry became wildly popular, to the point that United States mines were overwhelmed by the demand. Once again, Native American traders had to start importing Persian turquoise. This time, buyers focused on particular artisans and skilled jewelry makers such as Robert Sorrell, Charles Loloma, Lambert Homer, and Porfilio Sheyka. Most turquoise jewelry on the market today, particularly if it is affordable, is imitation turquoise, or low-grade turquoise treated to have a more attractive appearance. In fact, imitation turquoise goes back to the Victorians, who were the first to use glass to mimic the stone; it is difficult to distinguish from the real thing, but if you spot bubbles under the surface, you are looking at glass. Enamel turquoise tends to have a greater luster than real turquoise. Other stones like howlite, fossil bone, limestone, and chalcedony are stained and sold as turquoise, too. In 1972, a French company called Gilson produced imitation turquoise in the lab, and even gave it the spiderweb matrix. Natural turquoise may also be treated. Reconstructed or pressed turquoise is made of turquoise powder or chips mixed with liquid plastic resin, which is then dyed and baked. This cheap material can be identified by looking at it under magnification or heating it, as it will reveal a burning plastic smell. Most real American turquoise may turn green in response to light, oil, heat, and water, so it should be treated with care. Because it is more porous than Persian turquoise, American turquoise is stabilized by soaking it in resin or impregnating it with wax. This is to keep it from crumbling and does not affect the value. Enhanced turquoise is dyed to improve its color and luster, but the effect is temporary, so this kind of turquoise is much cheaper. In this case, you can see the difference in color just by scratching the surface.