Image: <a href="//commons.wikimedia.org/wiki/User:Cccefalon" title="User:Cccefalon">CEphoto, Uwe Aranas</a> (CC BY-SA 4.0)
orthorhombicuncommonsilicates
Prehnite
Ca₂Al(AlSi₃O₁₀)(OH)₂
A geode featuring pale green, translucent, botryoidal to radiating aggregates of Prehnite crystals encrusting a darker, possibly limonite-stained base.
Prehnite Physical Properties
Mohs Hardness
6Crystal System
orthorhombicLuster
vitreousStreak Color
whiteCleavage
good on {001}Fracture
unevenSpecific Gravity
2.85Colors
green, yellow-green, white, grayTransparency
transparentType Locality
Karoo Basin, South AfricaMineral Group
silicatesUses
jewelry, collector, ornamentalAssociated Minerals
zeolites, calcite, epidote, quartz, copperRarity
uncommonGeological Context
Prehnite typically forms as a secondary mineral filling vesicles and cavities in mafic igneous rocks, such as basalts and gabbros, and can also be found in low-grade metamorphic environments.
