Prehnite
Mineral Ca2Al(AlSi3O10)(OH)2
About it
Pale green botryoidal crusts and barrel-shaped crystal groups in basalt; Paterson, New Jersey, Mali (with black epidote), and Australia. The first mineral named after a person.
- Type
- Mineral
- Group
- Silicate (inosilicate), prehnite group
- Formula
- Ca2Al(AlSi3O10)(OH)2
- Hardness (Mohs)
- 6–6.5
- Specific gravity
- 2.8–2.95
- Streak
- white
- Lustre
- vitreous (glassy), pearly
- Crystal system
- Orthorhombic
- Colours
- pale green, yellow-green, white, grey, yellow
- Transparency
- transparent, translucent
- Cleavage and fracture
- good in one direction
Typical values: real specimens vary. For more, see mindat.org.