Yellow orange microcrystals of the extremely rare ammonium oxalate mineral oxammite, from one of the only four localities known worldwide (Petrogale Cave, Madura Roadhouse, Dundas Shire, Western Australia, Australia) and associated to minoritary aphthitalite. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Oxammite
Oxammite is an IMA-recognized mineral species in the organic mineral class, with the chemical formula (NH₄)₂(C₂O₄)·H₂O.
It crystallizes in the orthorhombic crystal system (space group P2_12_12). It is a member of the Oxalate structural group.
Key properties: Mohs hardness 2.5; specific gravity 1.5; optically biaxial.
IMA symbol Oxa, grandfathered status — known before the IMA’s founding, named in 1870.
Derived from bird or bat guano; in subfossil bird eggs and on subfossil birds.
It is found associated with Mascagnite (Guañape Islands, Peru).
As an OXalate of AMMonia.