Mimetite
Mimetite is one of the rarest of faceted gems since only one pocket of transparent crystals large enough for faceting has ever been found and very few of these crystals have been faceted. This ‘Gem Pocket’ was found at Tsumeb, Namibia in 1971 producing the finest, and largest Mimetite crystals in the world. Only crystals found in January 2003 at the Pingtouning Mine, Liannan, Sanjang, Guangdong China come close to those from Tsumeb. Even these are not nearly as large or gemmy though.
| Category: | Apatite group |
| Formula: | Pb5(AsO4)3Cl |
| Crystallography: | Hexagonal – Dipyramidal |
| Crystal Habit: | Crystals are usually prismatic to acicular, to 12 cm, may be tabular, rounded, barrel-shaped, mammillary, stalactitic, granular |
| Twinning: | On [1122], very rare |
| Cleavage: | [1011] Imperfect |
| Fracture: | Uneven to Subconchoidal |
| Tenacity: | Brittle |
| Hardness (Mohs): | 3.5 – 4.0 |
| Density: | 7.24 (g/cm3) |
| Luminescence: | May fluoresce reddish yellow under LW or SW UV |
| Radioactivity: | Not Radioacitve |
| Other: | Piezoelectric |
| Color: | Pale to bright Yellow, Yellowish Brown, Yellow-Orange, White, Colorless |
| Transparency: | Transparent, Translucent |
| Luster: | Resinous to Subadamantine |
| Refractive Index: | 2.128 – 2.147 Uniaxial ( – ); commonly anomalously Biaxial (–), sectored |
| Birefringence: | 0.019 |
| Dispersion: | n/a |
| Pleochroism: | Weak in Yellow shades |
