Agate
Image: <a href="//commons.wikimedia.org/wiki/User:Sailko" title="User:Sailko">Sailko</a> (CC BY-SA 3.0)
Mineral NameAgate
Chemical FormulaSiO2
Mohs Hardness6.5
Crystal Systemtrigonal
Streak ColorWhite
CleavageNone
FractureConchoidal
Specific Gravity2.6
Colorsorange, brown, black, white, yellow
TransparencyTranslucent
Type LocalityWorldwide, notable localities include Brazil, Uruguay, Mexico, Germany (Idar-Oberstein)
Mineral GroupSilicates
Usesjewelry, ornamental objects, collector's item, lapidary art
Associated Mineralsquartz, amethyst, calcite, zeolites
Raritycommon
Description
The image displays several polished, backlit slices of agate, showcasing intricate concentric and irregular banding patterns in various shades of orange, brown, black, yellow, and white, with some pieces featuring small central vugs lined with quartz crystals.
Geological Context
Agate typically forms in cavities (amygdules or geodes) within volcanic rocks, such as basalt, or in ancient lavas. Silica-rich fluids deposit successive layers of cryptocrystalline quartz (chalcedony) and other mineral impurities, creating the characteristic banded structure.
