Apophyllite

Real mineral · uncommon · KCa₄Si₈O₂₀(F,OH)·8H₂O

A hydrated potassium calcium silicate forming glassy prismatic crystals associated with zeolites in basaltic rocks. Its high water content causes it to exfoliate when heated. Frequently displays attractive combinations with stilbite and heulandite.

Identity

Formula

KCa₄Si₈O₂₀(F,OH)·8H₂O

Chemical class

silicate

Also known as

Fluorapophyllite, Hydroxyapophyllite

Crystallography

Crystal system

tetragonal

Habits

prismatic, tabular, pyramidal

Fracture

uneven

Physical properties

Mohs hardness

4.5

Density

2.35 g/cm³

Luster

vitreous, pearly

Colors

colorless, white, green, pink, yellow

Streak

white

Transparency

transparent, translucent

Geology

Origins

hydrothermal

Host rocks

basalt, gabbro

Associated minerals

Stilbite, Heulandite, Calcite, Prehnite

Geography

India (Pune region), USA, Canada, Germany, Iceland

Classification

Rarity

uncommon

Gem quality

No

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