Turquoise was one of the first gems to be mined. It was used by the Egyptians thousands of years ago. The color varies from green and greenish blue to sky blue. Color, matrix, and the mine from which it comes, determines the value. Turquoise is found in Iran, Sinai, China and the southwestern United States - Arizona, California, New Mexico, Colorado and Nevada. It is the birthstone of December. Most turquoise mined today is very chalky and only usable if stabilized.