Quartz

#7 hardness on Mohs scale, good toughness. Sources are Brazil(major source), India, Namibia, Sri Lanka, United States, Uruguay, Zambia. A closely related quartz variety called ametrine contains a striking mixture of two contrasting quartzes—purple amethyst and yellow citrine. Ametrine deposits are found in Brazil, and Bolivia. Amethyst has been the most prized member of the …