Black microcrystals of the extremely rare Cu vanadate fingerite associated to also black mcbirneyite from the TL for both minerals in Izalco volcano in El Salvador, in a matrix of green colored anhydrite probably colored by copper inclusions. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Fingerite
A triclinic copper vanadate deposited as fumarole sublimates in the crater of El Salvador's Izalco volcano.
Intro adapted from Wikipedia (CC BY-SA).
Fingerite is an IMA-recognized mineral species in the vanadate class, with the chemical formula Cu₁₁O₂(VO₄)₆.
It crystallizes in the triclinic crystal system (space group P-1).
Key properties: specific gravity 4.776; Dark reddish brown streak; Metallic luster; optically biaxial.
IMA symbol Fgr, IMA status: approved, named in 1983.
A rare component of vanadium-bearing sublimates in fumaroles on a basaltic volcanic cone, formed between 100 ° C and 200 ° C.
It is found associated with Thenardite, euchlorine, stoiberite, shcherbinaite, ziesite, bannermanite, chalcocyanite, chalcanthite.
In honor of Dr. Larry W. Finger (1940–), American mineralogist, Carnegie Institution, Washington, D.C., USA.