Apophyllite
Image: S. Rae from Scotland, UK (CC BY 2.0)
Mineral NameApophyllite
Chemical FormulaKCa₄(Si₄O₁₀)₂F·8H₂O
Mohs Hardness4.5
Crystal Systemtetragonal
Lustervitreous
Streak Colorwhite
Cleavageperfect on {001}
Fractureuneven
Specific Gravity2.35
Colorscolorless, white, green
Transparencytransparent
Type LocalityIndia
Mineral GroupPhyllosilicates
Usescollector, decorative
Associated Mineralsstilbite, heulandite, scolecite, calcite, quartz
Raritycommon
Description
The exhibit features Apophyllite in two forms: a geode-like specimen with small, sparkling colorless to white crystals, and a large specimen showcasing vibrant green, blocky crystals forming bands on a white matrix.
Geological Context
Apophyllite typically forms in the vesicles and amygdales of basaltic volcanic rocks, often in association with various zeolite minerals. It is also found in some hydrothermal veins.
