The SiO2 Gemstone Family

Quartz is the most popular and widely used gemstone of the SiO 2 family with its phenomenal varieties and spectacular colors, e.g., near-colorless (rock crystal), purple (amethyst), yellow (citrine), smoky (smoky quartz), and pink. The colors of these varieties are mostly caused by trace contents of foreign ions, which in turn are activated by treatment with high-energy radiation and/or…