Ferruccite (white) on Avogadrite (yellow-brownish), picture size: 5 mm Locality: Vesuvius, Italy — Photo: Thomas Witzke · CC BY-SA 3.0 de
Avogadrite
Avogadrite ((K,Cs)BF4) is a potassium-caesium tetrafluoroborate in the halide class. Avogadrite crystallizes in the orthorhombic system (space group Pnma) with cell parameters a 8.66 Å, b 5.48 Å and c Å 7.03.
Intro adapted from Wikipedia (CC BY-SA).
Avogadrite is an IMA-recognized mineral species in the halide class, with the chemical formula KBF₄.
It crystallizes in the orthorhombic crystal system (space group Pbnm). It is a member of the Baryte structural group.
Key properties: specific gravity 2.9; refractive index 1.324; optically biaxial.
IMA symbol Avg, grandfathered status — known before the IMA’s founding, named in 1926.
Formed as a sublimation product around volcanic fumaroles.
It is found associated with Sassolite, malladrite, hieratite (Vesuvius, Italy).
The name refers to Amedeo Avogadro (1776–1856), Professor of Physics at the University of Turin, Turin, Italy.