Prehnite
Image: Robert M. Lavinsky (CC BY-SA 3.0)
Mineral NamePrehnite
Chemical FormulaCa₂Al(AlSi₃O₁₀)(OH)₂
Mohs Hardness6.5
Crystal Systemorthorhombic
Lustervitreous
Streak Colorwhite
CleavageGood on {001}
Fractureuneven
Specific Gravity2.9
Colorspale green, yellowish-green, white, gray
Transparencytranslucent
Type LocalityMerelani Hills (Mererani), Lelatema Mts, Arusha Region, Tanzania
Mineral GroupSilicates
Usesjewelry, carvings, collector specimens
Associated Mineralszeolites, apophyllite, calcite, epidote, copper
Rarityuncommon
Description
This specimen displays a pale green, botryoidal aggregate of Prehnite, exhibiting a translucent quality. The surface has a smooth, rounded appearance typical of its growth habit.
Geological Context
Prehnite typically forms as a secondary mineral in veins and cavities of mafic igneous rocks like basalts and gabbros, often associated with low-grade metamorphic conditions. It can also be found in some metamorphic rocks.
