DO YOU KNOW YOUR TURQUOISE?

When you purchase turquoise, do you know what you are really getting?



Because turquoise is one of the most preferred stones of many cultures, it is often imitated, faked or doctored. How do we know which one we are really buying if the seller is not educated in the types of turquoise or is trying to sell an imitation.



The first turquoise was mined in Egypt, but the stones were low grade and the mines were quickly depleted. Later a higher grade of turquoise was discovered in Persia (now Iran) and was routed through Turkey to European countries. The modern name turquoise is derived from the French word for Turkish. Today most turquoise is mined in the United States and China.



Colors of turquoise range from green to blue in natural stones that are mined in the U.S. and have a variety of matrix patterns. Turquoise is somewhat porous and its original color can be changed through the absorbtion of moisture, skin oils, hand lotions, and perfumes.



Less than 10% of all mined turquoise qualifies as gem-grade; over time this stone will hold its color and hardness due to the silica content. Therefore, most available turquoise has been treated or enhanced.



Stabilization is the most common form of enhancement. This process impregnates soft chalk turquoise with polymer resin to stabilize the color and harden the stone for polishing. The resin usually deepens the color giving the stone an appearance of natural turquoise.



A second method of enhancement involves use of an electrical process that deposits silica into the structure of the stone to simulate the hardness and density of natural gem-grade turquoise.



Imitation turquoise can range from plastic and glass to dyed and stabilized magnesite or howlite. Magnesite and howlite are porous and can accept dye, plus these stones have similar matrix patterns. African turquoise is dyed jasper, and Chinese yellow turquoise is actually serpentine.



It is almost impossible to detect electrically treated turquoise. Your best action is to ask the seller to disclose the true nature of the turquoise they are selling; reputable dealers are willing to do so.



Turquoise ranges from 5 to 7 in Mohs hardness. Do not use soap or solvents to clean it; use a soft cloth and lukewarm water. Avoid excessive exposure to heat or sunlight as it can dry out the stone causing cracks and/or color fading.



This information was obtained from an article in the March 2010 Art Jewelry magazine entitled "Turquoise: One of the most imitated stones" by Richard M. Shull, G.G.