Turquoise is a hydrated form of copper aluminum phosphate. The presence of copper in the stone gives turquoise its characteristic blue color. The dark dendritic pattern seen on the surface of the rock represents the remnants of the parent bedrock within which the turquoise was formed. Although copper and aluminum are key constituents of turquoise, other substances are also present in varying but trace quantities. In some cases, these other elements can influence the color of the specimen. Other elements present in trace quantities may alter the color of turquoise. Turquoise usually has a specific gravity of about 2.7, and is moderately hard with a Mohs hardness ranging from 5 to 6. Most turquoise must be stabilized before it can be used in turquoise pendants and other jewelry. Stabilization is usually done by infusing the stone with epoxy resin or vaporized silica. Sometimes, a dye is added to the resin in order to modify the color of the stone. Stabilization using vaporized silica represents the current state of the art in jewelry design. For fiscal reasons however, epoxy resin is the most commonly used stabilizing agent.
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