Apophyllite specimens are found in ancient lava and basalt flows.
Layman's explanation:
Apophyllite is also known as fish-eye stone. It is essentially white, with a vitreous luster, but may show shades of green, yellow, or red. The composition is variable but approximates to KFCa4(Si2O5)4· 8H2O. It resembles the zeolites, with which it is sometimes classified, but differs from most zeolites in having no aluminum. It occurs as a secondary mineral in cavities in basic igneous rocks, commonly associated with zeolites. Apophyllite specimens are found in ancient lava and basalt flows. The crystals grow in the now solid cavities, called amygdules or vesicles, formed by air bubbles when the rock was molten. Apophyllite exfoliates (swell) when heated, therefore, it loses water and tends to peel or flake. The symmetry is tetragonal and the crystal structure contains sheets of linked SiO4 groups.
Citation of a publication:
American Mineralogist. 56 (1971)
p1222-1233;Colville,A.A. Anderson,C.P.
IUPAC name:
Sodium Potassium Calcium Fluorosilicate Hydrate
Lab name:
Common molecules
Sample provider:
Obtained from the Inorganic Crystal Structure Database
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