Outstanding yellow crystals of laphamite associated to white crystal aggregates of the also very rare K silicofluoride mineral hieratite. From: Shamokin, Northumberland County, Pennsylvania, United States of America. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Hieratite
Hieratite is an IMA-recognized mineral species in the halide class, with the chemical formula K₂SiF₆.
It crystallizes in the cubic crystal system (space group Fm-3m).
Key properties: Mohs hardness 2.5; specific gravity 2.665; Vitreous luster.
IMA symbol Hie, grandfathered status — known before the IMA’s founding, named in 1882.
Found as a deposit around volcanic fumaroles.
It is found associated with Sassolite, mirabilite, glauberite, selenian sulfur, realgar, alums (Vulcano, Italy); avogadrite, malladrite (Vesuvius, Italy).
Its name comes from the Greek Hiera, an ancient name for Vulcano.