Heulandite

Real mineral · uncommon · (Ca,Na)₂-3Al₃(Al,Si)₂Si₁₃O₃₆•12(H₂O)

A zeolite of basalt cavities, growing in coffin-shaped tablets with a pearly sheen on the cleavage. Like every zeolite it holds water loosely in an open framework, and gives it up on gentle heating.

Identity

Formula

(Ca,Na)₂-3Al₃(Al,Si)₂Si₁₃O₃₆•12(H₂O)

Chemical class

silicate

Mineral group

Analcime, Natrolite, Stilbite

Also known as

Heulandite-Ca

Crystallography

Crystal system

monoclinic

Habits

tabular, prismatic

Fracture

uneven

Physical properties

Mohs hardness

3

Density

2.2 g/cm³

Luster

pearly, vitreous

Colors

white, reddish white, grayish white, brownish white, yellow

Streak

white

Transparency

transparent, translucent

Geology

Origins

igneous, hydrothermal

Host rocks

basalt, amygdaloidal lava

Associated minerals

Stilbite, Calcite, Natrolite, Analcime

Geography

India, Iceland, USA

Classification

Rarity

uncommon

Gem quality

No

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