The first thing to understand about today’s turquoise market is that 85% of available turquoise gemstones is treated in one form or another. The other 15% of turquoise is called “natural turquoise”. Natural turquoise is hard enough to shape, polish and set into jewelry without any treatments. Natural turquoise will demand a higher price due to its rarity.
The most common treatment is called “stabilization”. The medium and softer grades of turquoise are treated with resins and heated to make it hard enough to polish and enhance the beautiful blue and green colors of the stone. This is not a bad thing. Most turquoise for sale today is stabilized. It is durable, and the color will be maintained through years of wear.
Then we get into the other treatments such as fracture sealed, where resins are used to fill in cracks, enhanced, where matrix is created using a patented process and block, where turquoise crumbs are compressed and treated with resins to form into solid blocks.
I find that the easiest way to determine if a turquoise gemstone is natural or treated is with the “hot needle” test. When you heat a needle point red hot and place it on a natural turquoise gemstone, there will be no penetration or marking by the needle point. Treated turquoise, on the other hand will allow small penetration by the needle point and you may also smell the resin. I would suggest that you find an area on the gemstone that is not clearly visible while wearing it to perform this test, as the penetration is small but permanate.