Prehnite
Chemical Formula	Ca2Al(AlSi3O10)(OH)2
Species	Silicates
Crystal System	Orthorhombic
Mohs Scale	6
Specific Gravity	2.8-2.95
Color	Colorless to gray to yellow, yellow-green or white
Streak	White
Luster	Vitreous, Pearly
Refractive Index	n = 1.611 - 1.632 n = 1.615 - 1.642 n = 1.632 - 1.665
Diaphaneity	Translucent
Cleavage	Distinct/GoodGood on , poor on
Fracture	Irregular/Uneven
Crystal Habit：Globular, reniform to stalactitic
Geological Setting：A secondary mineral in mafic volcanic rocks, low grade metamorphic mineral.