Judging quality
Look for translucent gooseberry green and a smooth undamaged botryoidal surface. Prehnite with epidote from Mali is a benchmark association.
Silicate
Prehnite
Botryoidal green silicate with a soft grape-cluster surface, frequently hosting black epidote needles that make the best specimens.
Care
Reasonably durable. Warm soapy water is safe.
History & lore
The first mineral ever named after a person: Colonel Hendrik von Prehn, who brought it from the Cape in 1788.
Cultural history, recorded as tradition rather than as medical or scientific claim.
Common questions about Prehnite
- What is Prehnite?
- Botryoidal green silicate with a soft grape-cluster surface, frequently hosting black epidote needles that make the best specimens.
- How hard is Prehnite and what is it made of?
- Prehnite is a Silicate-family mineral with the composition Ca2Al2Si3O10(OH)2. It crystallizes in the orthorhombic system and rates 6-6.5 on the Mohs hardness scale. It occurs in green, yellow-green.
- Where does Prehnite come from?
- Notable localities for Prehnite include Mali, Australia, South Africa, China.
- How do you tell good Prehnite from filler?
- Look for translucent gooseberry green and a smooth undamaged botryoidal surface. Prehnite with epidote from Mali is a benchmark association.
- How do you care for Prehnite?
- Reasonably durable. Warm soapy water is safe.
See it in person
Photographs only go so far
Both rooms are open six days a week, and there is always someone happy to pull pieces out of the case so you can compare them under the light.