Turquoise Mining
Two of the main areas for turquoise mining are Arizona and Mexico. Turquoise mines in Arizona include Bisbee Turquoise, Castle Dome (Pinto Valley), Gleeson/Courtland, Ithaca Peak, Kingman, Morenci, Sleeping Beauty, and Turquoise Mountain.Turquoise mining in Mexico takes place mainly in the northern state of Sonora, and its mines include Caridad Mine, Barraca Mine, and Mun. de Baviacora.Also mines in Nacozari and Cananea ,Sonora ,Mexico.Baja California also has produced turquoise.
Processing of Turquoise
Most turquoise has been treated by processes such as plastic bonding, chemical vapor penetration, paraffin, or a different stabilizing agent. It has been estimated that only 3-10% of all mined turquoise is strong enough to be used without some form of stabilizing treatment. If left untreated, the majority of turquoise will soak in chemicals from the environment, causing the color to take on more of a green hue over time.
Many different types of treatments exist for turquoise stones, one of the most common being stabilization. This is the process of hardening the stone, usually by adding a polystyrene plastic resin into its pores, thereby sealing the color of the stone. This process may be substituted by oil or wax treatment, but will result in a far inferior product as the oil and wax do not give permanent results.
Some turquoise may also be color-treated, a process similar to that of stabilization, but with the addition of a color-enhancing dye. Color-treated dye may have a less natural, more plastic appearance. The color infusion process will likely result in a more blue, polished stone.
Treatment may also take the form of reconstitution. In this process, turquoise powder is combined with chips mixed with plastic resin along with coloring agents and then compressed. This type of processing results in a highly unnatural look which only vaguely resembles the natural turquoise stone.
Cutting of Turquoise
Turquoise is often cut into a cabochon in order to be used in various types of jewelry. Cabochon is a term that refers to a gemstone which has been shaped and polished rather than faceted, a technique commonly used on opaque stones, such as turquoise. Turquoise that is cut into a cabochon takes the form of a convex obverse with a flat reverse. This form of cutting also makes the turquoise stone more resistant to scratches and noticeable imperfections of the like. Cabochons are usually cut into an ellipse as the human eye cannot easily observe small asymmetries within this structure as it can with rounded shapes.
The process of cutting turquoise into a cabochon starts with a slab of rough rock and a slab saw, and the shape is stenciled from a template. The slab is trimmed using a trim saw and is then grinded down using diamond impregnated or silicon carbide wheels. The shaping can then be completed by hand by a process known as “dopping,” adhering the stone with hard wax onto a dop stick, which is then ground to the template line. Finally, the top of the turquoise stone is sanded and polished, usually into the shape of a dome.
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