May 29 2014
Umohoite, having a triclinic crystal system, was first discovered in Utah, USA. It was named for the things in its composition: uranyl, molybdate, hydrogen, and oxygen.
Properties of Umohoite
The following are the key properties of Umohoite:
- Cell Data
- Space Group: P1
- a = 6.3748(4)
- b = 7.5287(5)
- c = 14.628(1)
- α = 82.64(1)°
- β = 85.95(1)°
- γ = 89.91(1)°
- Z = 4
Or
- Space Group: P1
- a = 6.372(3)
- b = 7.535(4)
- c = 14.69(3)
- α= 97.1°
- β= 85.9°
- γ= 90.07°
- Z = 4
- Crystal Data
- Triclinic
- Pseudorhombohedral
- Point Group: 1 or 1
- Tabular plates, to 0.5mm, in rosettes
- Massive, in thin veinlets, and disseminated
- X-ray Powder Pattern: 4.13 (10), 3.20 (5), 3.15 (4), 12.2 (3), 6.18 (3), 2.07 (3), 3.11 (2)
- Chemical Composition
| Elements |
Content 1 |
Content 2 |
Content 3 |
| UO3 |
57.65 |
55.35 |
61.38 |
| MoO3 |
28.23 |
34.80 |
30.89 |
| H2O |
14 |
[8.85] |
7.73 |
| As2O3 |
1 |
- |
- |
| MgO |
- |
1 |
- |
| Total |
100.00 |
[100.00] |
100.00 |
- Optical Properties
- Optical Class: Biaxial (–)
- Pleochroism: X = dark blue; Y = pale blue; Z = olive-green
- Orientation: Y = b; X ^ c ≈ 9°05'; Z˜a
- Dispersion: r > v
- α = [1.66(1)]
- β = 1.831(5)
- γ = 1.915(5)
- 2V(meas.) = 65(2)°
- Estimated Properties
| Electron density |
Bulk density (electron density) = 4.06 g/cm3
note: Specific gravity of Umohoite = 4.74 g/cm3 |
| Photoelectric |
PEUmohoite = 1444.54 barns/electron
U = PEUmohoite x ρElectron density = 5869.21 barns/cm3 |
| Fermion index |
Fermion index = 0.05
Boson index = 0.95 |
Radioactivity
|
Umohoite is radioactive
|
How to Identify Umohoite
Umohoite can be found in black, bluish-black or dark green colors. It is opaque, with a blue-gray streak, and sub metallic luster. It can be observed in tabular, rosette, or platy forms.
The relative hardness of umohoite is 2, and its average density is 4.74 g/cm3.
Global Distribution
Umohoite is distributed in the following places:
- Freedom No. 2 mine, Marysvale, Ohio
- Piute Co. Utah
- Lucky Mc mine, Gas Hills, Fremont Co. Wyoming
- Alyce Tolino mine, Cameron
- Coconino Co. Arizona
- Shinkolobwe, Katanga Province, Congo
- Rab´ejac and Mas-d’Alary uranium deposits, south of Lod`eve, H´erault, France
- Kyzylsai Mo–U deposit, Chu-Ili Mountains, south-western Balkhash region, Kazakhstan
- Unspecified localities in the former Soviet Union
Occurrence of Umohoite and Useful Mineral Association
Umohoite occurs in sediment-hosted uranium-bearing deposits, formed in the oxidation zone above the water table.
It is closely associated with quartz, gypsum, pyrite, fluorite, calcurmolite, rutherfordine, uranophane, schoepite, iriginite, jordisite, ilsemannite, and uraninite.
References