Aug 29 2013
Bassetite was named after the Basset mine group, Cornwall, England, where it was first described. It belongs to the Meta-autunite group.
Properties of Bassetite
The following are the key properties of bassetite:
- Cell Data
- Space group: P21/m
- a = 6.98(4)
- b = 17.07(4)
- c = 7.01(7)
- β = 90°32(5)’
- Z = 2.
- Crystal Data
- Monoclinic, pseudo-tetragonal.
- Point group: 2/m.
- Crystals, with square or rectangular outline, to 3 mm, are thin tablets, flattened on [010], showing {111}, {101}, {110}, {001}, {010}.
- Typically in parallel or fan-like groups.
- Twinning: Two or more individuals at ~90° with [001] of one individual || [100] of the other.
- Common.
- X-ray powder pattern: 4.89 (10), 3.46 (10), 8.59 (6), 2.20 (6), 4.24 (3), 4.05 (3), 2.96 (3).
- Chemical Composition
| Elements |
Content 1 |
Content 2 |
Content 3 |
| UO3 |
61.99 |
62.71 |
61.51 |
| P2O5 |
15.21 |
15.43 |
15.26 |
| H2O |
14.49 |
14.20 |
15.50 |
| FeO |
7.60 |
7.78 |
7.73 |
| insol. |
0.63 |
- |
- |
| CuO |
0.28 |
- |
- |
| Total |
100.20 |
100.12 |
100.00 |
- Optical Properties
- Optical class: Biaxial (-)
- Pleochroism: X = Y = yellow; Z = dark olive-brown to brownish black
- Orientation: X = b; Y ^ c = 18.5
- Dispersion: r > v, strong
- α = 1.603(2); β = 1.610(2); γ = 1.617(2)
- 2V(meas.) = ~90°.
- Estimated Properties
| Electron density |
Bulk density (electron density) = 3.31 g/cm3
note: Specific gravity of bassetite = 3.70 g/cm3 |
| Photoelectric |
PEBassetite = 1,300.50 barns/electron
U = PEBassetite x ρ electron density = 4,304.94 barns/cm3 |
| Fermion index |
Fermion index = 0.0051266163
Boson index = 0.9948733837 |
|
Radioactivity
|
Bassetite is not radioactive.
|
How to Identify Bassetite
Bassetite can be identified in the field by its color variations such as bronze, brownish yellow, greenish brown, yellow, and olive green. Its transparent form has {010} perfect cleavage. This mineral has a vitreous luster with greenish white streak. The density of bassetite is 3.63 g/cm3 with a hardness of 2.5 – approximate to a finger nail.
Global Distribution
Bassetite is distributed in the following places:
- England - From the Basset group of mines, Illogan, and the South Terras mine, St. Stephen-in-Brannel, Cornwall.
- Italy - At Arcu su Linnarbu, Capoterra, near Cagliari, Sardinia.
- Spain - At the Los Ratones and Pedro Alvaro vanadium mines, Salamanca Province.
- Belgium - From Daverdisse.
- France - From the La Crouzille mine, Haute-Vienne.
- USA - On Overland Mountain, Jamestown district, Boulder Co., Colorado; in Utah, from the Denise No. 1 mine and in the Fuemrol mine, Temple Mountain, Emery Co., Utah; in Arizona, at the Sue and Red Bluff mines, Sierra Ancha Mountains, and widespread in the Dripping Springs quartzite in the northwestern part of Gila Co.; from the Merry Widow mine, Grant Co., New Mexico.
Occurrence of Bassetite and Useful Mineral Association
Bassetite occurs in a rare secondary mineral in the oxidized zone of some uranium-bearing hydrothermal mineral deposits. It is often associated with minerals such uranospathite, uraninite, pyrite, torbernite, meta-autunite, torbernite, saleeite, and metanovacekite.
References