TTO 0052 Turquoise Cabochons Three turquoise cabochons set in a silver-tone decorative rectangular frame. Probably 1940s. The brooch measures about 1 1/2" by 3/4" Turquoise was among the first gems to be mined, and while many historic sites have been depleted, some are still worked to this day. These are all small-scale, often seasonal operations, owing to the limited scope and remoteness of the deposits. Most are worked by hand with little or no mechanization.