Sep 26 2013
Boltwoodite was named after Bertram Borden Boltwood (1870-1927), radiochemist of Yale University, New Haven, Connecticut, USA, who devised the U-Pb method of measuring geologic time.
Properties of Boltwoodite
The following are the key properties of boltwoodite:
- Cell Data
- Space group: P21
- a = 7.073(2)
- b = 7.064(1)
- c = 6.638(1)
- β = 105°45 (1)’
- Z = 2
- Crystal Data
- Monoclinic
- Point group: 2
- Radiating acicular to fibrous, elongated along [010], to 1 cm
- X-ray powder pattern: 6.81 (100), 3.40 (90), 2.95 (80), 3.54 (70), 2.91 (70), 6.40 (50), 5.45 (50)
- Chemical Composition
| Elements |
Content 1 |
Content 2 |
Content 3 |
| UO3 |
68.5 |
67.19 |
66.64 |
| SiO2 |
14.8 |
13.27 |
14.00 |
| K2O |
9.4 |
7.83 |
10.97 |
| H2O |
6.9 |
- |
8.39 |
| LOI |
- |
6.91 |
- |
| Na2O |
0.4 |
2.54 |
- |
| CaO |
- |
1.59 |
- |
| Fe2O3 |
- |
0.52 |
- |
| Total |
[100.0] |
99.85 |
100.00 |
- Optical Properties
- Optical class: Biaxial (-)
- Pleochroism: Weak; X = colorless; Y = Z = yellow; anomalous blue interference colors
- α = 1.668-1.670; β = 1.695-1.696; γ = 1.698-1.703
- 2V(meas.) = Large
- Estimated Properties
| Electron density |
Bulk density (electron density) = 3.19 g/cm3
note: Specific gravity of Boltwoodite = 3.62g/cm3 |
| Photoelectric |
PEBoltwoodite = 1,429.97barns/electron
U=PEBoltwoodite x ρ electron density= 4,558.55 barns/cm3 |
| Fermion index |
Fermion index = 0.0071947992
Boson index = 0.9928052008 |
| Radioactivity |
Boltwoodite is radioactive |
How to Identify Boltwoodite
Boltwoodite can be identified in the field by its color variations between yellow and light yellow. Its opaque form has {010} perfect and {001} distinct cleavage. This mineral has a vitreous-pearly luster with white streak. The density of boltwoodite is 3.6 g/cm3, with a hardness of 3.5-4 - between that of a copper penny and fluorite.
Global Distribution
Boltwoodite is distributed in the following places:
- USA - From the Delta mine, Emery Co., Utah; the New Method mine, near Amboy, San Bernardino Co., California; in the Marshall Pass district, at the Little Indian No. 36 mine, Gunnison Co. and the Lookout No. 22 mine, Saguache Co., and in Unaweep Canyon, Mesa Co., Colorado; in the Green Monster mine, Goodsprings district, Clark Co., Nevada; and in the Williams quarry, near Easton, Northampton Co., Pennsylvania
- Namibia -Exceptionally developed at the Raossing mine, near Swakopmund
- Rwanda - At Karago
- Argentina - From Quebrada del Tigre, Cordoba Province, and near Guandacol, La Rioja Province
- Scotland - From near Dalbeattie, Kirkcudbrightshire
- Australia - From near Myponga, South Australia
- Japan- In the Togo mine, Tottori Prefecture
Occurrence of Boltwoodite and Useful Mineral Association
Boltwoodite occurs in the outer silicate zone of alteration surrounding hydrated uranyl oxides incrusting primary uraninite; and also filling fractures at some distance from primary uraninite. It also occurs in pegmatite and Colorado-Plateau-type sandstone uranium deposits.
Boltwoodite is often associated with minerals such as uraninite, becquerelite, fourmarierite, gypsum, fluorite, and phosphouranylite.
References