Rare ammonium-Mg-phosphate mineral dittmarite from the type locality in Australia: Skipton Caves, Mount Widderin, Corangamite Shire, Victoria, Australia. Ex Vandenbroucke Museum collection specimen, from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Dittmarite
Dittmarite is an IMA-recognized mineral species in the phosphate class, with the chemical formula (NH₄)Mg(PO₄)·H₂O.
It crystallizes in the orthorhombic crystal system (space group Pmn2_1).
Key properties: specific gravity 2.15; optically biaxial.
IMA symbol Dmr, grandfathered status — known before the IMA’s founding, named in 1887.
Found in dryer parts of bat guano in caves.
It is found associated with Struvite, newberyite, hannayite, schertelite (Skipton lava tube caves, Australia); swaknoite, mundrabillaite, arcanite (Arnhem Cave, Namibia).
The mineral was named to honor William Dittmar (1833–1892), Professor of Chemistry, University of Glasgow, Glasgow, Scotland.