Stibiotantalite
Stibiotantalite is a mineral consisting of Sb(Ta,Nb)O4 (antimony, tantalum or niobium, and oxygen). It is found in complex granite pegmatites.[1]
| Stibiotantalite | |
|---|---|
 | |
| General | |
| Category | Oxide minerals |
| Formula (repeating unit) | Sb(Ta,Nb)O4 |
| Strunz classification | 04.DE.30 |
| Dana classification | 08.01.06.02 |
| Crystal system | orthorhombic |
| Space group | mm2 |
| Unit cell | a = 4.9, b = 11.79, c = 5.57Å, Z = 4; V = 321.78 |
| Identification | |
| Formula mass | 336.70 |
| Colour | yellow to dark brown, reddish |
| Fracture | brittle-conchoidal |
| Mohs scale hardness | 5.5 |
| Streak | light yellow |
| Diaphaneity | transparent to translucent |
| Density | 6 to 7.57 |
| Refractive index | 1.55 - 1.69 |
| Birefringence | Biaxial (+), a=2.3742, b=2.4039 |
| 2V angle | 75.083 |
| Dispersion | strong |
If the quantity of niobium exceeds the tantalum content, the mineral is called stibiocolumbite.[2]
It is translucent to transparent, medium hard (5.5 mohs), appears yellow to dark brown, reddish or greenish brown, with an adamantine luster.
Stibiotantalite is found in veins and walls associated with tin mines. It is a fairly rare to rare mineral. Due to its relative softness, it is more likely to be found in mineral collections than in jewelry.[2]
References
- "Stibiotantalite Mineral Data". Web Mineral. Retrieved March 9, 2019.
- "Stibiotantalite Value, Price, and Jewelry Information". International Gem Society. Retrieved March 9, 2019.
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