Prehnite
Species
Uncommon · Ca₂Al(AlSi₃O₁₀)(OH)₂
A calcium aluminium silicate forming in the vesicles and fractures of basaltic rocks. Often found with zeolites and pectolite as part of low-grade metamorphic mineral assemblages. Its pale green botryoidal masses are distinctive.
Identity
- Formula
- Ca₂Al(AlSi₃O₁₀)(OH)₂
- Chemical class
- Silicate
Crystallography
- Crystal system
- Orthorhombic
- Habits
- Tabular, Botryoidal, Massive
- Fracture
- Uneven
Physical properties
- Mohs hardness
- 6
- Density
- 2.92 g/cm³
- Luster
- Vitreous, Pearly
- Colors
- pale green, yellow-green, gray, white
- Streak
- white
- Transparency
- Translucent, Transparent
Geology
- Origins
- Hydrothermal, Metamorphic
- Host rocks
- Granite, Volcanic rock, Schist and gneiss
- Associated minerals
- zeolite, Pectolite, Calcite, Epidote
- Geography
- South Africa, Namibia, Australia, USA, Canada
Classification
- Rarity
- Uncommon
- Gem quality
- Yes
Sources
- M. Pasero and others, IMA Commission on New Minerals, Nomenclature and Classification, The New IMA List of Minerals, updated September 2026. International Mineralogical Association (CNMNC), 2026.
- Prehnite. Mindat.org (Hudson Institute of Mineralogy).
- J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols, Prehnite. Mineral Data Publishing, Handbook of Mineralogy, 2001.
- Prehnite. Gemdat.org (Hudson Institute of Mineralogy).
- Prehnite. Wikipédia, l'encyclopédie libre (fr).
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