Agate
Image: Hannes Grobe (CC BY-SA 2.5)
Mineral NameAgate
Chemical FormulaSiO2
Mohs Hardness7
Crystal Systemtrigonal
Lustervitreous
Streak Colorwhite
Cleavagenone
Fractureconchoidal
Specific Gravity2.65
Colorsreddish-brown, orange, white
Transparencytranslucent
Type LocalityWorldwide, notably Brazil, Uruguay, Mexico
Mineral GroupSilicates
Usesjewelry, ornamental, industrial, collector
Associated Mineralsquartz, calcite, zeolites
Raritycommon
Description
A translucent reddish-brown agate showing a central cavity (geode) lined with tiny, sparkling quartz crystals, creating a 'D' shape.
Geological Context
Agate typically forms in the vesicles of volcanic rocks or in cavities of sedimentary rocks, where silica-rich fluids deposit successive layers of chalcedony.
