May 28 2014
Theisite is a rare secondary mineral in fahlore deposits. The mineral was first discovered in Durango, La Plata County, Colorado, USA.
It was named after Nicholas J. Theis, a geologist at the Bendix Corporation.
Properties of Theisite
The following are the key properties of Theisite:
- Cell Data
- Space Group: n.d
- a = 8.220–8.225
- b = 7.123
- c = 14.934–15.019
- Z = 2
- Crystal Data
- Orthorhombic (probable), pseudohexagonal
- Point Group: n.d
- Crystal cleavage plates are usually curved or crumpled, to 2mm; may be micaceous, lamellar, in spherical aggregates and crusts
- X-ray Powder Pattern: 3.741 (10), 14.97 (9), 2.534 (9), 7.483 (5), 1.830 (5), 1.533 (5), 4.112 (4)
- Chemical Composition
| Elements |
Content 1 |
Content 2 |
Content 3 |
| CuO |
33.3 |
34.32 |
33.97 |
| ZnO |
33.1 |
35.83 |
34.50 |
| As2O5 |
14.8 |
14.06 |
13.03 |
| H2O |
10.5 |
- |
- |
| Sb2O5 |
7.0 |
8.11 |
9.92 |
| CaO |
0.3 |
- |
- |
| Total |
99.0 |
|
|
- Optical Properties
- Optical Class: Biaxial (–), nearly uniaxial (–)
- α = 1.755
- β = 1.785
- γ = 1.785
- 2V(meas.) = ≈0°
- Estimated Properties
| Electron density |
Bulk density (electron density) = 4.07 g/cm3
note: Specific gravity of Theisite = 4.30 g/cm3 |
| Photoelectric |
PETheisite = 48.41 barns/electron
U = PETheisite x ρElectron density = 196.91 barns/cm3 |
| Fermion index |
Fermion index = 0.01
Boson index = 0.99 |
Radioactivity
|
Theisite is not radioactive
|
How to Identify Theisite
Theisite can be found in green or blue-green colors. It has a translucent form and perfect cleavage. It has a tendency to form aggregates made of a number of individual clusters or crystals. Its fractures appear like curved scrapings or shavings produced by a knife blade.
The density of theisite is 4.3 g/cm3, and its relative hardness is 4.3.
Global Distribution
Theisite is distributed in the following places:
- Tucker’s tunnel uranium deposit, near Durango, Hinsdale Co. Colorado, USA
- Tynagh mine, near Loughrea, Co. Galway, Ireland
- Glucksrad mine, Oberschulenberg, Harz Mountains, Germany
- Richelsdorf Mountains, Hesse
- Clara mine, near Oberwolfach, Black Forest
- Padern, Pyr´en´ees-Orientales, France
- Sa Duchessa mine, Oridda district, Italy
- Is Murvonis mine, Domusnovas, Sardinia
- Canale Fondone, near Forno, Piedmont
- Brixlegg, Tirol, Austria
Occurrence of Theisite and Useful Mineral Association
Theisite occurs as a rare secondary mineral in thin seams cutting other oxidized minerals (near Durango, Colorado, USA), and in dolomitized marble (Forno, Italy).
References