The Different Treatments Given to Turquoise
By Sonia Acone
Turquoise is a hydrated copper aluminum phosphate that, in its natural state, resembles the striking blue coloring of a Robin’s egg (or greenish-blue when iron impurities are present). Natural Turquoise is quite soft (only 5-6 on the Mohs scale), porous and brittle. Its color will remain stable as long as it is not exposed to high temperatures, direct sunlight, oils, perspiration, cosmetics or household chemicals. Over time, natural Turquoise will fade in coloring and even turn yellow.
Because of its porous, fragile and brittle nature, much of the Turquoise on the market today has been treated or altered in some way to retain or enhance its durability and coloring. There is not necessarily anything wrong with treated Turquoise, as long as the seller/manufacturer discloses such treatments to its customers.
Below are some of the treatments used to enhance natural Turquoise.
This is Turquoise that is hardened by injecting polystyrene plastic resins, paraffins, etc. into the stone under high pressure and heat. The result is a harder stone that can withstand more handling as well as a blue color that is locked in and will retain that color for a longer period of time. Much of the Turquoise on the market today has been stabilized, since natural Turquoise is so brittle and soft.
This type of treatment involves taking tiny pieces of Turquoise, grounding them down into a powder and then bonded with resins and dyes, resulting in a solid piece that can be cut and polished. Most often, some reconstituted Turquoise contains little or no actual Turquoise at all, but simply dyes and resins. Another name used to describe reconstituted Turquoise is “Block Turquoise” or "Chalk Turquoise".
There are some manufacturers in Asia that are adding unnatural coloring agents to achieve weird and strange colors such as yellow, pink, purple and bright apple-green and claiming that they have discovered “new” varieties of Turquoise. Buyer beware!
Dyed turquoise is basically the same process used in stabilization, but dyes are used to enhance the color. Unfortunately, the color of dyed Turquoise is a bit too-blue and looks highly-polished or “plastic”. Waxing and Oiling are also used to enhance a stone’s color, where waxes and oils are added to cracks in the stone; however, these are not long-lasting and the stone will eventually lose its color.
Backing involves taking very thin blades of Turquoise that are too small to stand alone and adding an extra material (stone, etc.) to the back to add strength. It can then be cut, shaped and polished.
Beware of Imitations
Stones such as Howlite and Magnesite, which are naturally white and porous, are often dyed and sold as Turquoise. Jasper, Marble and varieties of Chalcedony are sometimes dyed to resemble Turquoise as well. Other stones that may be sold as Turquoise but aren’t, include Chrysocolla, Variscite, and Lazulite.