Hieratite

hieratite

avogadrite

malladrite

sassolite

Images

Formula: K₂SiF₆
Fluoride, paramorph of demartinite
Crystal System: Isometric
Specific gravity: 2.665 measured, 2.668 calculated
Hardness: 2½
Colour: Colourless, white, grey; colourless in transmitted light
Solubility: Soluble in cold water; more so in hot water.
Environments

Fumeroles

All of the known host rocks for hieratite are potassium-bearing igneous rocks, some of which contain abundant K-feldspar and/or leucite. Clearly, the field occurrence indicates that hieratite is formed under surface or near-surface conditions by the chemical reaction of HF vapour or HF-bearing solutions with K-feldspar, leucite, or cryptocrystalline potassium-bearing igneous rocks (AM 57.287-291).

Localities

At the Vesuvius fumaroles, Mount Vesuvius, Somma-Vesuvius Complex, Naples, Campania, Italy, hieratite is associated with avogadrite and malladrite (HOM).

At the type locality, La Fossa crater, Vulcano Island, Lipari, Eolie Islands, Metropolitan City of Messina, Sicily, Italy, hieratite occurs in active volcanic fumaroles, associated with sassolite, mirabilite, glauberite, selenium-bearing sulphur, realgar and alums (HOM).

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