CS Book 5_AS- 25 Lapis Lazuli:Opaque Gems .pdf

Colored Stones 25 KEY CONCEPTS Lapis lazuli is valued for its history and rich blue color. Iron causes turquoise to appear greenish blue, while copper creates the more desirable pure blue color. The presence of lazurite pro...

Colored Stones 25 KEY CONCEPTS Lapis lazuli is valued for its history and rich blue color. Iron causes turquoise to appear greenish blue, while copper creates the more desirable pure blue color. The presence of lazurite produces lapis lazuli’s prized royal blue color. Matrix-free and spiderweb turquoise command the highest prices. Lapis value is based on color and the presence or absence of calcite or pyrite. Turquoise is most often cut into cabochons, but it might also Lapis might be dyed, impregnated with wax or plastic, or be cut into beads or flat pieces for inlays. heated and then dyed. Turquoise that’s porous and coarse is commonly treated to Afghanistan is the world’s major source of lapis lazuli as well improve color and texture. as the major source of the gem’s best color. The southwestern US is the world’s largest producer of The world market for lapis is steady, prices are low, and turquoise, while China’s Hubei Province is the major source of availability is good. its top color. Glass, plastic, and ceramic materials have all been used as The largest, most consistent turquoise market is the American lapis imitations. Southwest. People value turquoise for its combination of ancient heritage and attractive color. It’s important to be on the lookout for plastic turquoise imitations, which are common in the market. Turquoise is judged by its color, texture, and matrix. Some translucent to opaque gemstones are prized as An intense, uniform, medium blue is turquoise’s most-prized ornamental materials because of their exotic colors and color. distinctive markings. Key Terms Reconstructed turquoise—A turquoise imitation made of Stabilized turquoise—A trade term for polymer- a mixture of powdered minerals, dyed and bonded with impregnated turquoise. plastic or epoxy resin. Spiderweb turquoise—Turquoise that contains matrix in thin, web-like patterns. 210