Agate
Image: Hannes Grobe (CC BY-SA 2.5)
Mineral NameAgate
Chemical FormulaSiO2
Mohs Hardness7
Crystal Systemtrigonal
Streak Colorwhite
Cleavagenone
Fractureconchoidal to uneven
Specific Gravity2.65
Colorsyellow, orange, brown, white, black
Transparencytranslucent
Type LocalityWorldwide (e.g., Brazil, Uruguay, Mexico, USA)
Mineral GroupSilicates
Usesjewelry, ornamental objects, collector, industrial
Associated Mineralsquartz, amethyst, calcite, zeolites
Raritycommon
Description
This image displays a polished cross-section of agate, revealing intricate, wavy bands of varying shades of yellow, orange, brown, and white, with some darker, almost black, outer layers. Several irregular cavities, or vugs, lined with tiny crystalline structures are visible within the banded matrix.
Geological Context
Agate forms primarily in the cavities of volcanic rocks, such as basalt, where silica-rich solutions deposit successive layers of chalcedony. It can also be found in some metamorphic and sedimentary rocks, often filling voids left by dissolved organic matter or other minerals.
