A lot of white single crystals of the very rare minerals fairchildite and bütschliite from a locality in Ontario: Desoronto, Richmond Township, Lennox & Addington County, Ontario, Canada. Fairchildite and Bütschliite are two very rare K-Ca carbonates. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Bütschliite
Bütschliite is an IMA-recognized mineral species in the carbonate class, with the chemical formula K₂Ca(CO₃)₂.
It crystallizes in the hexagonal crystal system (space group R-3m).
Key properties: specific gravity 2.607; optically uniaxial.
IMA symbol Büt, grandfathered status — known before the IMA’s founding, named in 1947.
Formed in fused wood-ash clinkers in partly burned trees.
It is found associated with Calcite, fairchildite.
The mineral was named to honor Johann Adam Otto Bütschli (1848–1920), Professor of Zoology at the University of Heidelberg, Heidelberg, Germany, who studied double salts of potassium and calcium.