Prehnite
Pale green botryoidal silicate, the first mineral named after a person.
- Family
- Prehnite
- Formula
- Ca₂Al₂Si₃O₁₀(OH)₂
- Mohs
- 6 to 6.5
- System
- Orthorhombic
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Science
Prehnite grows in cavities of basalt as rounded, grape-like clusters and fans of tabular crystals, often with black tourmaline or epidote needles inside. Its colour is from a little iron. It is one of the minerals that forms during low-grade metamorphism of volcanic rocks.
- Mineral
- Prehnite
- Formula
- Ca₂Al₂Si₃O₁₀(OH)₂
- Crystal system
- Orthorhombic
- Mohs hardness
- 6 to 6.5
- Specific gravity
- 2.80 to 2.95
- Refractive index
- 1.610 to 1.670
- Lustre
- Vitreous to pearly
- Colours
- Pale green, Yellow-green
Composition
Ca₂Al₂Si₃O₁₀(OH)₂. Made of Calcium, Aluminium, Silicon, Oxygen, Hydrogen, with trace Iron responsible for colour.
Origin
- AustraliaWave Hill
- MaliKayes, with epidote
- South AfricaCape, type locality
- United StatesNew Jersey
- China
- Scotland
Filled dots are primary sources
Rarity
Plentiful as crusts; translucent gem material for cutting is uncommon.
- 1 Abundant
- 2 Common
- 3 Uncommon
- 4 Rare
- 5 Exceptional
Hardness
Prehnite sits at 6 to 6.5 on the Mohs scale. Glass and a knife blade are about as hard; it wears well with care.
Energy
Associations from crystal-healing tradition, recorded here as folklore. They are not medical claims.
Chakras
- Heart
- Solar Plexus
Element
- Earth
Zodiac
- Libra
- Virgo
Planets
- Venus
Properties
- Unconditional love
- Preparedness
- Calm
- Dream work
Lore
Named in 1788 for Colonel Hendrik von Prehn, who brought it from the Cape of Good Hope: the first mineral named for a person. Its lore is entirely modern, framed around the 'healer's healer'.
Modern practice pairs it with epidote as a stone for anticipating what is needed.
- FirstFirst mineral named after a person, 1788.
- HabitBotryoidal, from the Greek for bunch of grapes.