In the case of quartz, for example, yellow quartz (citrine) has trace amounts of ferric iron (Fe 3+), rose quartz has trace amounts of manganese, purple quartz (amethyst) has trace amounts of iron, and milky quartz, which is very common, has millions of fluid inclusions (tiny cavities, each filled with water).
20 Common Minerals Cochise College Geology Home Page. Roger Weller, geology instructor [email protected] ... Milky quartz is usually massive, but well