May 13 2014
Simpsonite was first discovered in 1938 from the Tabba Tabba, Western Australia. It was named after Edward Sydney Simpson, a Western Australian government mineralogist and analyst.
Properties of Simpsonite
The following are the key properties of Simpsonite:
- Cell Data
- Space Group: P3
- a = 7.385–7.387
- c = 4.515–4.516
- Z = 1
- Crystal Data
- Hexagonal
- Point Group: 3
- Euhedral to subhedral crystals, tabular to short prismatic, with {1010} and {0001}, and rarely a few other forms, striated || [0001], to 2.4cm; commonly in subparallel groups
- X-ray Powder Pattern: 1.651 (100), 2.859 (67), 3.69 (62), 2.131 (59), 1.395 (54), 2.417 (40), 2.609 (37)
- Chemical Composition
| Elements |
Content 1 |
Content 2 |
Content 3 |
| Ta2O5 |
71.54 |
76.4 |
64.6 |
| Al2O3 |
25.20 |
22.8 |
24.3 |
| Nb2O5 |
1.82 |
- |
8.6 |
| SiO2 |
1 |
- |
- |
| FeO |
0.16 |
- |
- |
| CaO |
0.12 |
- |
- |
| SnO2 |
0.10 |
- |
0.9 |
| TiO2 |
0.02 |
- |
- |
| H2O |
- |
1 |
1.1 |
| Total |
99.96 |
100.2 |
99.5 |
- Optical Properties
- Optical Class: Uniaxial (–)
- ω = 2.045(5)
- ε = 2.025(5)
- Estimated Properties
| Electron density |
Bulk density (electron density) = 5.63 g/cm3
note: Specific gravity of Simpsonite = 6.35 g/cm3 |
| Photoelectric |
PESimpsonite = 629.45 barns/electron
U = PESimpsonite x ρElectron density = 3543.83 barns/cm3 |
| Fermion index |
Fermion index = 0.0001
Boson index = 0.9998 |
Radioactivity
|
Simpsonite is not radioactive
|
How to Identify Simpsonite
Simpsonite is either colorless, or occurs in different colors. These range from light yellow to light brown, white and brownish-yellow. It is a transparent, fluorescent mineral having vitreous luster and white streak. Its fractures are brittle, producing small, conchoidal fragments. It can be formed as prismatic, euhedral crystals, or parallel lines on a crystal surface. The hardness of simpsonite ranges from 7 to 7.5, and its density is 6.7 g/cm3.
Global Distribution
Simpsonite is distributed in the following places:
- Tabba Tabba, Western Australia
- Alto do Giz pegmatite, near Parelhas, and the Onca mine, about 25km distant, Rio Grande do Norte, Brazil
- Al Hayat and Mdara mines, Bikita; at the Benson No. 3 pegmatite, Mtoko, Zimbabwe
- Mumba, near Lake Kivu, Kivu Province and Manono pegmatite, Katanga, Congo
- Leshaia pegmatite, Vuoriyarvi carbonatite complex, Kola Peninsula, Russia
- Tanco pegmatite, Bernic Lake, Manitoba, Canada
Occurrence of Simpsonite and Useful Mineral Association
Simpsonite occurs as an uncommon accessory mineral in some tantalum-rich granite pegmatites.
Quartz, muscovite, tourmaline, eucryptite, petalite, pollucite, montebrasite, spodumene, beryl, tapiolite, microlite, manganotantalite, and tantalite are all closely associated with simpsonite.
References