These last sapphires are embedded in clay lenses (feldspar altered to kaolinite) and are surrounded by biotite mica and chlorite (figure 4). Prospecting is done by local geologists. Figure 3.

How the author of a new Marsha P. Johnson biography lives out Black trans joy Texas Isiah for Tourmaline; Courtesy Penguin Random House Tourmaline; MARSHA: The Joy and Defiance of Marsha P. Johnson ...

Copper-bearing gem tourmaline, known as Paraíba tourmaline after the location of its original discovery, is prized for its vivid blue to green color. This article explains GIA’s use of quantitative ...