Agate
Image: “Jon Zander (Digon3)” (CC BY-SA 3.0)
Mineral NameAgate
Chemical FormulaSiO2
Mohs Hardness7
Crystal Systemtrigonal
Lustervitreous
Streak Colorwhite
Cleavagenone
Fractureconchoidal
Specific Gravity2.6
Colorsgrey, white, bluish-grey, brown, black
Transparencytranslucent
Type LocalityWorldwide
Mineral GroupSilicates
Usesjewelry, ornamental objects, lapidary, collector
Associated Mineralsquartz, calcite, zeolites
Raritycommon
Description
A polished, banded rock exhibiting curvilinear layers of translucent grey, white, and darker tones, typical of agate.
Geological Context
Agate forms in cavities of volcanic rocks, where silica-rich fluids deposit successive layers of chalcedony, often with varying impurities causing the distinct banding.
