Stabilized turquoise is created by adding a clear resin to chalk, or soft, turquoise to help enhance the color and well as increase the hardness of the stone. Chalk, or soft, turquoise is usually a lower grade of turquoise as it is too soft to be used on its own for jewelry and must be stabilized with resin. Since turquoise is a very porous substance, the resin fills in the tiny holes and crevices to form a firm stabilized turquoise stone.
Most turquoise is treated in some way. Natural untreated turquoise is actually quite rare, as only about three percent of the turquoise sold in the world is mined and sold without anything being added to it. The term treated turquoise is used to mean any turquoise that is stabilized with dyed resin rather than clear. Treated turquoise is usually less expensive than either natural or stabilized turquoise, but it may look artificial in color.
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 keeps, the color of the stone the same no matter how much it is worn next to the skin. Stabilized turquoise costs less than natural turquoise, but is still considered beautiful and desirable.
Stabilized turquoise differs greatly from reconsituted turquoise. Reconstituted turquoise is the cheapest type of turquoise. It is a soft, or chalk, turquoise powder that has a great deal of resin and dye added to the powder. This mixture is then pressed into blocks and cut into many different shapes. Imitation turquoise contains no turquoise at all, not even soft, or chalk, turquoise. Either just dyed resin is used to make imitation turquoise or the dyed resin is added to a white stone such as howlite.
It's important for turquoise buyers to know what they're getting since it's 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 actually mostly resin, the pin will sink way into the piece and leave a mark. The turquoise buyer should always get a signed receipt from the seller as to what type of turquoise he/she is supposed to be selling.