Durangite - Encyclopedia
Class : Phosphates, arsenates, vanadates
Subclass : Anhydrous arsenates
Crystal system : Monoclinic
Chemistry : NaAl(AsO4)F
Rarity : Very rare
Durangite is a very rare sodium and aluminum arsenate, whose genesis seems linked to pneumatolytic emanations. It is in fact known in veins cutting alkaline rhyolites with tridymite, in pegmatite dykes and high temperature veins with cassiterite and topaz. It owes its name to its discovery location : the Barranca tin mine in the state of Durango (Mexico). Durangite commonly forms automorphic crystals, up to 3 cm maximum, with rough faces, red-orange to dark red in color, sometimes yellow in various shades.
Main photo : Durangite from Thomas Range, Utah, USA © Dan Weinrich
Durangite in the World
Twinning
No twin known for this mineral species.
Fakes and treatments
No fake listed for this mineral species.
Hardness : 5.5
Density : 3.94 to 4.07
Fracture : Irregular
Streak : Yellow
TP : Translucent
RI : 1.634 to 1.685
Birefringence : 0.051
Optical character : Biaxial -
Pleochroism : Visible
Fluorescence : None
Solubility : Sulfuric acid
Magnetism : None
Radioactivity : None