Ferberite
Ferberite is a member that is rare of Wolframite mineral series that also includes Hübnerite. Hübnerite could be the manganese end that is rich while Ferberite is the Iron rich end member and Wolframite is the intermediate between your two. Ferberite is a small ore of Tungsten which is an important element that is industrial. Notable occurrences include Bolivia; Asia; England; Germany; Peru; Russia; South Korea; and Colorado, Idaho, New Mexico and South Dakota, USA.
| Category: | Tungstate mineral |
| Formula: | FeWO4 |
| Iron(II) Wolframate | |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | Crystals are wedge-shaped, typically flattened and elongated, to 15 cm; faces striated; in groups of bladed crystals; massive |
| Twinning: | Contact twins with composition plane; also interpenetrant or lamellar |
| Cleavage: | [010] Perfect, [100] Parting, [102] Parting |
| Fracture: | Uneven |
| Tenacity: | Brittle |
| Hardness (Mohs): | 4.0 – 4.5 |
| Density: | 7.50 – 7.60 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Other: | Slightly Magnetic |
| Color: | Black, Dark Brown on thin edges |
| Transparency: | Nearly Opaque to Opaque; Transparent on thin edges |
| Luster: | Adamantine, Metallic, Sub Metallic |
| Refractive Index: | 2.255 – 2.414 Biaxial ( + ) |
| Birefringence: | 0.1590 |
| Dispersion: | Extreme; r > v |
| Pleochroism: | n/a |
| Anisotropism: | Distinct; bBireflectance: weak |
