Turquoise is a very expensive stone which is the major reason why there are a lot of imitation stones on the market. Turquoise originally was mined in Iran (Persia) but now a great deal of it comes from the Sleeping Beauty mines in Arizona. China, Brazil, and Russia are also another source of turquoise stones. The best turquoise comes from Arizona. The color of turquoise ranges from china blue, deep blue to blue-green, dark greenish blue and yellowish green. Normally, turquoise may contain a matrix also known as the mother stone which penetrates it in the form of veins of various colors such as brown, black, and ochers.
Ideally, turquoise shouldn't contain any matrix. The quality of turquoise is based upon the color, its intensity, and the presence of any matrix. A piece of turquoise from the Sleeping Beauty mines that is free of matrix with an intense blue color is considered the ideal material.
As the turquoise stone ages, it becomes darker in color and turns a slightly green color. It can also crack due to light, oils, or a loss of water content. Detergent, grease and perspiration can also discolor the turquoise stone.
Turquoise can also be treated with various methods. One method involves reconstructing or pressing turquoise. Turquoise powder and small chips are bonded with liquid plastic resin, dyed and then baked. Once the material is solid, it can be cut into any shape. Some turquoise stones especially the ones from America are very porous so in order to add more stability to the stone, the turquoise is soaked in artificial resin or it's impregnated with wax to improve its color and harden its surface. Another method of enhancing the color of turquoise is to dye it or stain it. Oil, paraffin and copper salt can also be used but the results are temporary.
Hardness: 5-6 Mohs
Specific Gravity: 2.80
Refractive Index: 1.61-1.65
Crystal Form: Triclinic. It's opaque to semi-translucent, has a waxy to dull luster, and a high porosity which means that it can fade and crack over time. It has a conchoidal fracture which means that it can crumble and get scratches very easily.