What is Stabilized Turquoise
Turquoise consists of two primary compounds - hydrated phosphates of copper and aluminum. In addition, most specimens of turquoise also contain varying amounts of iron, zinc, and silica. The blue color of your sterling silver turquoise pendant comes from its copper content. The dark veins that you see on the surface of the stone are remnants of the rock that played host to the formation of turquoise. The secondary compounds present within the matrix of the stone can influence its physical characteristics. Iron and zinc tend to change the blue color of the stone to green and yellow, respectively. Silica plays a crucial role in the physical characteristics and properties of the stone. Most silica is naturally infused with some amount of silica. This infusion occurred millions of years ago during the early formation stages of turquoise. In some cases, the infusion was complete and the molten silica bound the copper and aluminum salts together, creating a specimen that was hard, durable, and could hold a shine. In other instances, the infusion of silica was partial or insignificant. In such cases, the resulting stone was porous, had a low density, and relatively soft and fragile. Most of the turquoise mined today is of the latter variety and is generally considered to be directly used in jewelry. The stone must first be stabilized.
There are a wide range of methods available to stabilize turquoise today. The two best methods use epoxy resin, or silica vapors. In the case of epoxy stabilization, the stone is immersed in liquid resin for a few days. Due to capillary action, the liquid is sucked into the stone for a distance of about a few millimeters. The stone is then removed from the liquid and allowed to dry in the air. The dried stone is harder and takes a better shine than the untreated stone. In some cases, the infusion of the resin is enhanced by using a combination of vacuum and pressure. The penetration of the resin is deeper, and a larger volume of the stone is stabilized. Epoxy resin stabilization is by far the most popular method to stabilize turquoise today, and it is quite likely that the turquoise beads in your white pearl necklace were stabilized using epoxy resin. The second method is to use silica vapors to stabilize the stone. This is a far more complex process and must be done under controlled laboratory conditions. Furthermore, proper health and safety measures are needed because exposure to silica vapors can be hazardous. The method is also significantly more expensive and involved compared to epoxy stabilization. The quality of the stabilized stone however, is much better than specimens stabilized with resin. Even experienced gemologists and jewelers find it difficult to distinguish natural turquoise from silica vapor stabilized turquoise.