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Stabilized turquoise is created by adding a clear resin to chalk or soft turquoise to help bring out the color and also increase the hardness of the stone. Chalk, or soft turquoise, is usually a lower grade of turquoise, as it is too soft to use alone in jewelry and must be stabilized with resin. Since turquoise is a very porous substance, the resin fills in the small holes and cracks to form a firm and stabilized turquoise stone.
Most turquoise is treated in some way. Untreated natural turquoise is actually quite rare, as only about 3% of the turquoise sold in the world is mined and sold without anything added to it. The term treated turquoise is used to refer to any turquoise that is stabilized with tinted rather than clear resin. Treated turquoise is usually cheaper than natural turquoise or stabilized turquoise, but can be artificially colored.
Natural turquoise changes color the more it is worn as it reacts with the oils in the skin. Stabilized turquoise, on the other hand, stabilizes or maintains the same color as the stone, no matter how much it is worn on the skin. Stabilized turquoise costs less than natural turquoise, but is still considered beautiful and desirable.
Stabilized turquoise differs greatly from reconstituted turquoise. Reconstituted turquoise is the cheapest type of turquoise. It is a soft turquoise powder, or chalk, that contains a large amount of resin and dye added to the powder. This mix is then pressed into blocks and cut into many different shapes. Imitation turquoise contains no turquoise, not even soft turquoise, no chalk. Dyed resin is used to make an imitation turquoise or dyed resin is added to a white stone such as howlite.
It is important for turquoise buyers to know what they are buying, as it is not always easy to tell how much resin something sold as turquoise actually contains. One test is to heat a pin and place it on the turquoise. If the stone is mostly resin, the pin will sink into the piece and leave a mark. The turquoise buyer should always obtain a signed receipt from the seller stating what type of turquoise they are selling.