Image: <a rel="nofollow" class="external text" href="https://www.flickr.com/people/47445767@N05">James St. John</a> (CC BY 2.0)
trigonalcommonSilicates
Agate
SiO2
A cut and polished agate nodule, 11.0 cm across, displaying concentric bands of translucent microcrystalline quartz (chalcedony) in shades of brown, white, and grey.
Agate Physical Properties
Mohs Hardness
6.5Crystal System
trigonalLuster
vitreousStreak Color
whiteCleavage
noneFracture
conchoidalSpecific Gravity
2.6Colors
white, grey, brown, clearTransparency
translucentMineral Group
SilicatesUses
jewelry, ornamental, collectorAssociated Minerals
Rarity
commonGeological Context
Agate forms in cavities of volcanic rocks, often as geodes that have completely filled with microcrystalline quartz through rhythmic deposition of silica-rich solutions. Impurities in different layers cause variations in color.
