Ferberite's the iron endmember of the manganese - iron wolframite solid solution series. The manganese endmember's hübnerite. Ferberite's a black monoclinic mineral composed of iron(II) and tungstate, FeWO4. Ferberite occurs as granular masses and as slender prismatic crystals. It's a Mohs hardness of 4.5 and a specific gravity of 7.4 to 7.5. Ferberite typically occurs in pegmatites, granitic greisens and high temperature hydrothermal deposits. It's a minor ore of tungsten. It was discove… (More on Ferberite)