Prehnite
Image: Ivar Leidus (CC BY-SA 4.0)
Mineral NamePrehnite
Chemical FormulaCa₂Al(AlSi₃O₁₀)(OH)₂
Mohs Hardness6
Crystal Systemorthorhombic
Lustervitreous
Streak Colorwhite
Cleavagegood on {001}
Fractureuneven
Specific Gravity2.87
Colorspale green, yellowish-green
Transparencytranslucent
Type LocalitySouthbury, Connecticut, USA
Mineral GroupSilicates
Usescollector, jewelry
Associated Mineralsquartz, calcite, epidote, zeolites
Rarityuncommon
Description
This specimen features botryoidal to reniform aggregates of pale yellowish-green prehnite, forming rounded masses on a dark matrix with some white crystalline material.
Geological Context
Prehnite typically forms in the vesicles and cavities of mafic igneous rocks (such as basalt and diabase) during low-grade metamorphic or hydrothermal alteration processes.
