Ferberite

Mineral FeWO4

About it

The iron-rich wolframite: black, very heavy, and weakly magnetic, with a dark streak. Bladed crystals come from Panasqueira in Portugal and Bolivia, and the Boulder County tungsten district of Colorado mined it.

Type
Mineral
Group
Tungstate, wolframite group
Formula
FeWO4
Hardness (Mohs)
4–4.5
Specific gravity
7.4–7.6
Streak
brownish black to black
Lustre
submetallic, metallic
Crystal system
Monoclinic
Colours
black
Transparency
opaque
Cleavage and fracture
perfect in one direction; uneven fracture
Magnetic
Weakly

Typical values: real specimens vary. For more, see mindat.org.