Tarbuttite
Tarbuttite is a rare zinc phosphate mineral that belongs to the Olivenite Group of minerals that also includes Adamite. Tarbuttite is typically rather unattractive, even ugly by mineral specimen standards. It has been referred to as a bat-poop mineral since it often forms in ancient caves under layers of mineral-rich bat guano deposited over tens of thousands of years. However, specimens from the Skorpion Mine in the Rosh Pinah, Lüderitz District, Karas Region of Namibia are different. Crystals from a new find there in 2007 are transparent, pastel green and gemmy.
Tarbuttite has been found at these localities: the type locality at Kabwe (Broken Hill), Zambia. In the Lueca vanadium mines, Angola. From the Kef Semmah mine, near Sétif, Algeria. In Australia, on Reaphook Hill, near Blinman, Flinders Ranges, South Australia; at Broken Hill, New South Wales. In the Hudson Bay mine, Salmo, British Columbia, Canada. At an undefined locality in Guangdong Province, China. The best crystals are from the Skorpion Mine, Rosh Pinah, Lüderitz District, Karas Region, Namibia.
| Chemical Formula: | Zn2(PO4)(OH) |
| Zinc Phosphate Hydroxide | |
| Molecular Weight: | 242.76 gm |
| Composition: | Zinc | 53.87 % | Zn | 67.05 % | ZnO |
| Phosphorus | 12.76 % | P | 29.24 % | P2O5 | |
| Hydrogen | 0.42 % | H | 3.71 % | H2O | |
| Oxygen | 32.95 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE | |||
| Crystallography: | Triclinic – Pinacoidal |
| Crystal Habit: | Crystals typically equant to short prismatic, complex, with many forms, to 2 cm; in sheaflike or saddle-shaped aggregates; as crusts. |
| Twinning: | None |
| Color: | Colorless, pale yellow, may be brown, red, or green; colorless in transmitted light. |
| Transparency: | Translucent to Transparent |
| Luster: | Vitreous, Pearly on cleavages |
| Refractive Index: | 1.659 – 1.713 Biaxial ( – ) |
| Birefringence: | 0.0530 |
| Dispersion: | Weak to Strong |
| Pleochroism: | Very Strong |
| Color: | Colorless, pale yellow, may be brown, red, or green; colorless in transmitted light. |
| Transparency: | Translucent to Transparent |
| Luster: | Vitreous, Pearly on cleavages |
| Refractive Index: | 1.659 – 1.713 Biaxial ( – ) |
| Birefringence: | 0.0530 |
| Dispersion: | Weak to Strong |
| Pleochroism: | Very Strong |
