Judging quality
Heulandite forms flat plates; stilbite forms sheaves. Look for pearly cleavage faces and clean crystal edges.
Zeolite
Heulandite
Tabular zeolite crystals in coffin-shaped plates, often orange-peach and frequently mistaken for stilbite, with which it shares its Indian localities.
Care
Soft and water-sensitive. Dust with a dry brush.
History & lore
Zeolites are industrially vital as molecular sieves and water softeners, a use derived from their open cage-like structures.
Cultural history, recorded as tradition rather than as medical or scientific claim.
Common questions about Heulandite
- What is Heulandite?
- Tabular zeolite crystals in coffin-shaped plates, often orange-peach and frequently mistaken for stilbite, with which it shares its Indian localities.
- How hard is Heulandite and what is it made of?
- Heulandite is a Zeolite-family mineral with the composition (Ca,Na)2-3Al3(Al,Si)2Si13O36·12H2O. It crystallizes in the monoclinic system and rates 3-3.5 on the Mohs hardness scale. It occurs in peach, white, green.
- Where does Heulandite come from?
- Notable localities for Heulandite include India, Iceland, Brazil.
- How do you tell good Heulandite from filler?
- Heulandite forms flat plates; stilbite forms sheaves. Look for pearly cleavage faces and clean crystal edges.
- How do you care for Heulandite?
- Soft and water-sensitive. Dust with a dry brush.
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.