THE MINERAL FERBERITE

Chemistry: FeWO4, Iron tungstate
Class: Sulfates
Subclass: Tungstates
Uses: as a minor ore of tungsten (an important industrial element) and as a mineral specimen
Specimens

Ferberite belongs to a series with another mineral, Huebnerite , MnWO4. Huebnerite is the Manganese rich end member while ferberite is the iron rich end member. Wolframite is the name of the series and the name applied to indistinguishable specimens and specimens intermediate between the two end members. Most specimens found in nature fall within 20 - 80% range of the series and these are termed wolframites, (Fe, Mn)WO4. Only if they are 80% or more iron are they called ferberite. Ferberite's iron content causes the dramatic differences between it and hubnerite (wolframite is of course intermediate). Ferberite tends to be black colored, with a black streak, is opaque with a nearly submetallic luster, is denser, has crystals with a different elongation and can be weakly magnetic. Huebnerite, however, tends to be light in color, with a lighter streak, more transparent and less dense. Ferberite is the rarer member of the series.

PHYSICAL CHARACTERISTICS:

Color is Black.
Luster is submetallic.
Transparency crystals are opaque.
Crystal System is monoclinic; 2/m
Crystal Habits include the flat, heavily modified, tabular crystals. The crystals are elongated along the b axis and are generally flattened in the a axis direction. Also as columnar aggregates and lamellar masses.
Cleavage is perfect in one direction parallel to the a and c axes.
Fracture is uneven.
Hardness is 4 - 4.5.
Specific Gravity is approximately 7.6 (heavy even for metallic minerals)
Streak is black.
Associated Minerals are quartz, hematite, tourmalines, cassiterite, micas and pyrite.
Other Characteristics: crystals are often striated.
Notable Occurrences include Nanling Range, China; South Dakota and Colorado, USA; Russia; Korea; England and Bolivia.
Best Field Indicators are crystal habit, color, density, luster and cleavage.

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