Fingerite

Fingerite is a copper vanadate mineral with formula: β-Cu₂V₂O₅. It was discovered as triclinic crystals occurring as volcanic sublimates around fumaroles in the crater of the Izalco Volcano, El Salvador.

Fingerite
Image of a Fingerite
General
Category	Vanadate mineral
Formula	β-Cu2V2O5
IMA symbol	Fgr[1]
Strunz classification	8.BB.80
Crystal system	Triclinic
Crystal class	Pinacoidal (1) H-M symbol: (1)
Space group	P1
Unit cell	a = 8.16, b = 8.27 c = 8.04 [Å]; α = 107.14° β = 91.39°, γ = 106.44°; Z = 1
Identification
Color	Black; medium gray in reflected light
Crystal habit	Subhedral or anhedral; equant or platelike; up to 150 μm
Cleavage	None
Luster	Metallic
Streak	Dark reddish brown
Diaphaneity	Opaque
Density	4.78
Optical properties	Biaxial
Solubility	Dissolves in water
References	[2][3][4]

Associated minerals include thenardite, euchlorine, stoiberite, shcherbinaite, ziesite, bannermanite, chalcocyanite and chalcanthite.^[2] The mineral also dissolves in water.^[5]

Fingerite is named for Dr. Larry W. Finger (1940–2024^[6]) of the Geophysical Laboratory, Carnegie Institution of Washington.