Gemstone profile and identification guide
Prehnite
Prehnite is a calcium aluminum silicate used as a translucent green gemstone and collector mineral.
Profile Navigation
Overview
Prehnite is a calcium aluminum silicate used as a translucent green gemstone and collector mineral.
Did you know? Prehnite was among the first minerals named after a person (Colonel Hendrik von Prehn).
Use this profile as a collector reference and educational guide for quick on-page comparison, then validate with the interactive identification system.
Identification
Name: Prehnite
Scientific classification: Silicate (Phyllosilicate: Prehnite)
Hardness: 6.25 Mohs
Transparency: translucent
Lustre: vitreous to pearly
Crystal system: Orthorhombic
Primary colour: Green
Secondary colour: Yellow Green
Colour family: Greens
Typical green tone, botryoidal habits, and prehnite optical constants are key indicators.
Verification Status
Status: verified-core-fields
Reference priority: GIA, Gem-A, Mindat, International Gem Society
Core identity, locality, and physical-property fields reviewed against standard gemological references.
Values are reported as practical gemological ranges where appropriate.
Physical Properties
Hardness category: hard
Hardness value: 6.25 Mohs
Chemical composition: Calcium aluminum silicate hydroxide [Ca2Al(AlSi3O10)(OH)2]
Crystal system: Orthorhombic
Common locations: South Africa, Australia, China, United States, Mali
Learn more: Gem-A gemstone education resources.
Colour Variations
Pale green to yellow-green translucent silicate, often in botryoidal or massive forms.
Optical effects: Chatoyancy (rare)
Detailed Gemology
Mineral species: Prehnite
Mineral group: Phyllosilicate group
Chemical formula: Calcium aluminum silicate hydroxide [Ca2Al(AlSi3O10)(OH)2]
Mohs hardness: 6.25
Crystal system: Orthorhombic
Lustre: vitreous to pearly
Transparency: translucent
Streak: White
Cleavage: Perfect in one direction
Fracture: Uneven to subconchoidal
Specific gravity: 2.80-2.95
Refractive index: 1.61-1.67
Optical phenomena: Rare chatoyancy
Colour range: Colorless to yellow-green and green
Common inclusions: Epidote needles, matrix inclusions, fractures
Geological environment: Hydrothermal and low-grade metamorphic environments
Principal mining regions: South Africa, Australia, China, United States, Mali
Important commercial sources: Commercial prehnite is sourced from South Africa and several global volcanic/metamorphic terrains
Historical significance: Used as decorative gemstone since the 18th century.
Common treatments: Generally untreated; occasional stabilization may occur.
Synthetic or imitation forms: Glass and dyed quartz imitations exist.
Common look-alikes: Chrysoprase, serpentine, jade-like materials
Jewellery uses: Used in cabochons, beads, carvings, and occasional faceted stones.
Care recommendations: Moderately durable; avoid hard impact and prolonged ultrasonic cleaning.
Cross-check profile data with GIA Gem Encyclopedia and Mindat entry for Prehnite.
Formation
Forms in low-grade metamorphic and hydrothermal environments, often in basalt cavities.
Origin
Commercial prehnite is sourced from South Africa and several global volcanic/metamorphic terrains
Uses
Best for: Used in cabochons, beads, carvings, and occasional faceted stones.
Ideal uses: Cabochons and carved jewelry emphasizing soft green translucency.
Care
Moderately durable; avoid hard impact and prolonged ultrasonic cleaning.
Need another candidate? Use advanced gemstone search or return to the identification guide.
Related gemstones by colour
Related gemstones by hardness
Commonly confused gemstones
Prehnite FAQ
How can I identify Prehnite?
Compare hardness (6.25 Mohs), crystal system (Orthorhombic), colour profile, and lustre (vitreous to pearly) with your sample. Then cross-check related gemstones listed above.
What colour range does Prehnite appear in?
Pale green to yellow-green translucent silicate, often in botryoidal or massive forms.
Where is Prehnite commonly used?
Cabochons and carved jewelry emphasizing soft green translucency.. For maintenance, follow the care guidance in this profile.
Scientific References
GIA: general gemstone identity (reviewed) - Batch 04 factual verification pass.
Gem-A: gemological terminology and testing references (reviewed) - Batch 04 factual verification pass.
Mindat: mineral species and principal localities (reviewed) - Batch 04 factual verification pass.
International Gem Society: gem trade context and treatment overview (reviewed) - Batch 04 factual verification pass.