You may know that turquoise is found in a variety of colors, ranging from a white to dark navy blue to lime green. But did you know that turquoise can actually change color?
Turquoise is a very porous and absorptive precious stone. When a turquoise stone is exposed to water, oils and other chemicals it soaks them up like a sponge. Contact with some of these foreign substances can have a variety of effects. Turquoise is a compound that includes metals such as aluminum, copper or iron. Water and oil can cause some of these metals to oxidize, or in other words rust. As a result of oxidation, the stones can actually change color. Blue turquoise that contains copper can change from a light blue to a dark green. The iron changes from green to darker green and aluminum from light blue to darker blues and greens.
The oils in our hands have a very similar affect as water. Over years, or even decades, of touching a turquoise stone with our fingers can lead to the stone changing color. Treatments of the stones called stabilization actually help prevent this process from happening. Though there are different methods and levels of stabilization their purpose is all the same, to protect the natural turquoise color and structure.
This phenomenon of turquoise stones changing color is often seen in vintage turquoise jewelry. Even though stabilization was used way back when ancient Egyptians used wax to coat their turquoise stones, most turquoise jewelry before the 1970s was made with natural stones. These pieces today display stones that are probably much darker in color than they originally may have been.