Amethyst
Image: <a href="//commons.wikimedia.org/w/index.php?title=User:%D7%99%D7%A9%D7%A8%D7%90%D7%9C_%D7%92%D7%A8%D7%99%D7%A0%D7%A2%D7%A8&action=edit&redlink=1" class="new" title="User:ישראל גרינער (page does not exist)">User:ישראל גרינער</a> (CC BY-SA 3.0)
Mineral NameAmethyst
Chemical FormulaSiO2
Mohs Hardness7
Crystal Systemtrigonal
Lustervitreous
Streak Colorwhite
Cleavagenone
Fractureconchoidal
Specific Gravity2.65
Colorspurple, violet, reddish-purple
Transparencytransparent to translucent
Type LocalityMinas Gerais, Brazil
Mineral GroupSilicates
Usesjewelry, ornamental, collector
Associated Mineralsquartz, feldspar, calcite
Raritycommon
Description
Amethyst is a beautiful purple to violet variety of quartz, often forming prismatic crystals or geodes. Its color is due to irradiation and iron impurities, and it is a popular gemstone.
Geological Context
Amethyst typically forms in hydrothermal veins, pegmatites, and in the cavities of volcanic rocks (geodes), crystallizing from silica-rich fluids at relatively low temperatures.
