Sussexite
Sussexite is a rare metamorphic borate mineral. It is an extremely rare gem. The mineral is typically found as translucent nodules or fibrous, matted aggregates, never transparent crystals. The pale pink material is attractive and would be an interesting addition to any rare gem collection. Sussexite is only found in a few locations worldwide but the facetable material is only found at Sterling Mine, Sterling Hill, Ogdensburg, Franklin Mining District, Sussex County, New Jersey, USA.
| Category: | Nesoborates |
| Formula: | MnBO2(OH) |
| manganese borate | |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | As bladed acicular crystals, to 7 mm; cross-vein or radial fibrous, in felted or matted aggregates, nodular. |
| Twinning: | Submicroscopic twinning on [100] which cannot be resolved optically. |
| Cleavage: | n/a |
| Fracture: | Sub-Conchoidal, Fibrous |
| Tenacity: | Brittle, Inflexible |
| Hardness (Mohs): | 3.0 – 3.5 |
| Density: | 3.30 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | White to Buff, Straw-Yellow, Pale Pink |
| Transparency: | Translucent |
| Luster: | Silky, Dull, Earthy |
| Refractive Index: | 1.670 – 1.732 Biaxial ( – ) |
| Birefringence: | 0.0620 |
| Dispersion: | Strong; r > v |
| Pleochroism: | None |
