Really outstanding crystals of the very rare organic mineral formicaite from one of the very few known localities worldwide (Alkali Lake, Lake County, Oregon, United States of America). Naturally occurring calcium formate - one of just two such minerals currently known (compare dashkovaite). Ex. Erich Laskowski collection (USA). — Photo: David Hospital · CC BY 4.0
Formicaite
Formicaite is an IMA-recognized mineral species in the organic mineral class, with the chemical formula Ca(CHOO)₂.
It crystallizes in the tetragonal crystal system (space group P4_12_12). It is a member of the Formate structural group.
Key properties: Mohs hardness 1; specific gravity 1.9; White streak; optically uniaxial.
IMA symbol Fmc, IMA status: approved, named in 1998.
Rare in hydrothermal veinlets cutting kurchatovite-sakhaite ore (Solongo deposit, Russia); in a veinlet in skarnitized marble (Novofrolovskoye deposit, Russia).
It is found associated with Calcite, lizardite, frolovite, pentahydroborite, hexahydroborite, vimsite (Solongo deposit, Russia); calcite, vesuvianite, pentahydroborite, frolovite.
Alludes to the composition, a calcium formate.