Turquoise prospector and metalsmith Dayton Simmons was in the SF Bay Area recently and gave a presentation about turquoise to the Metal Arts Guild. Thanks to him, I now know that the name comes from a long ago mistake in thinking the stones arriving in Europe were from Turkey, and that most turquoise comes from the first 100 to 200 feet of the Earth’s surface, and that copper rich turquoise is bluer than turquoise with copper and iron – which is more green.
In the past, I rarely bought turquoise because it’s so hard to know if the turquoise is natural. Dayton told us about the different processes for enhancing turquiose and how to tell some of them apart from natural turquoise.
A simple way to tell acrylic or epoxy impregnated turquoise from natural is to run your finger across it. The finger catches a little just as it does on plastic. A finger run across a piece of natural turquoise goes very smoothly. With a jeweler’s loop, one can look at the item in question and look for parallel lines versus random scratch lines. Parallel lines imply that the piece was shaped with lapidary equipment. Random scratch lines occur on “stabilized” pieces. A third way to tell is to run a knife blade across the piece. “Stabilized” pieces will scratch. The knife blade will leave carbon on the surface of a natural stone.
The finger test was enough to tell that these turquoise beads has been “stabilized” with acrylic.
If stabilization with acrylic or epoxy was the only method, that’s be easy. The Foutz Process, also called the Zachery Process, and the Eljen Process both modify natural turquoise to be harder than natural turquoise, so the knife test gives the same result for all three. Luckily, for now, sellers of Foutz / Zachery and Eljen turquoise are proud of their process and often label the pieces they are selling.
One other way to tell if a piece is processed is to ask for the source mine. Dayton Simmons shared that any turquoise coming out of China is treated without first determining if the turquoise would have been strong enough on its own. Sad. Certain US mine names imply certain treatment processes, and some stones are not from the mine they are being sold as coming from. For example, Valley Blue is often sold as coming from Dry Creek. Blue material coming out of southern China mimics Sleeping Beauty material coming out of the Kingman mine east of Phoenix. Certain turquoise look-a-likes, such as White Buffalo, are in reality a different stone. White Buffalo is calcite + quartz. Elat stone is Chrysicola. Â Hubblite sold in the past was Czech glass made to look like turquoise.
Dayton only sells natural turquoise, so I bought some pieces to use in future art jewelry pieces. I have a vague idea about combining some turquoise with orange sapphires.
Above are pieces of natural turquoise I purchased from Dayton which come from different mines in the US along with some Persian pieces. One of the pieces looks like the ocean, although someone else said it looks like the sky. The silver colored matrix material in some of the pieces is pyrite.