Turquoise is a hydrated copper and aluminum phosphate mineral. It is a cryptocrystalline mineral, meaning the structure is made up of microscopic crystals. Turquoise is opaque and has a waxy luster. It may appear semi-translucent in thin segments. Color is quite variable, ranging from white to a powder blue to a sky blue, and from a blue-green to a yellowish green. The blue is attributed to copper impurities while the green may be the result of either iron impurities or dehydration. Exposure to heat or sunlight is also detrimental to the color of the turquoise. The stone can be very porous and chalky, therefore it is usually treated prior to use in jewelry. The stones are “stabilized”, meaning they are treated with a resinous substance. Stabilizing the turquoise makes it less susceptible to chipping and keeps the color from changing due to contact with the oils in your body or moisture. Turquoise usually includes flecks of pyrite or is interspersed with dark, spidery yellowish-brown to black mineral veining known as matrix. Turquoise is rarely found without matrix, although Sleeping Beauty turquoise is often found in the pure form; they are vivid sky blue. The Sleeping Beauty mine is located in Arizona, USA.