Sep 25 2014
Brandtite was named after George Brandt (1694–1768), Swedish chemist. It belongs to the roselite group.
Properties of Brandtite
The following are the key properties of brandtite:
- Cell Data
- Space group: P21/c
- a = 5.897–5.899
- b = 12.991–12.968
- c = 5.964–5.684
- β = 108.01-108.05°
- Z = 2
- Crystal Data
- Monoclinic
- Point group: 2/m
- Stout to slender prismatic crystals, with prominent {100}, {110}, {120}, {010}, {122}, a number of minor forms, to 8 mm
- In radiated groups and fibrous spherules
- Twinning: On {100}, common
- X-ray powder pattern: 3.010 (100), 3.241 (70), 3.373 (55), 3.424 (30), 6.482 (25), 5.151 (20), 3.790 (20)
- Chemical Composition
| Elements |
Content 1 |
Content 2 |
Content 3 |
| As2O5 |
50.48 |
49.95 |
51.19 |
| CaO |
25.07 |
24.66 |
24.98 |
| MnO |
14.03 |
14.85 |
15.80 |
| H2O |
8.09 |
9.31 |
8.03 |
| PbO |
0.96 |
- |
- |
| MgO |
0.90 |
- |
- |
| FeO |
0.05 |
- |
- |
| P2O5 |
0.05 |
- |
- |
| Cl |
0.04 |
- |
- |
| insol. |
0.04 |
- |
- |
| Total |
99.71 |
99.23 |
100.00 |
- Optical Properties
- Optical Class: Biaxial (+)
- Orientation: X = b; Y ^ c = 6°; Z ^ c = 84°
- Dispersion: r < v, strong to very strong
- α= 1.707–1.709
- β= 1.711
- γ= 1.722–1.727
- 2V(meas.) = 15°-23°
- Estimated Properties
| Electron density |
Bulk density (electron density) = 3.52 g/cm3
note: Specific gravity of brandtite = 3.67 g/cm3 |
| Photoelectric |
PEBrandtite = 27.68 barns/electron
U=PEBrandtite x ρ electron density= 97.49 barns/cm3 |
| Fermion index |
Fermion index = 0.0017974823
Boson index = 0.9982025177 |
Radioactivity
|
Brandtite is not radioactive
|
How to Identify Brandtite
Brandtite can be identified in the field by its white color. It is sometimes colorless as well. Its transparent to translucent form has {010} perfect and {001} good cleavage. This mineral has a vitreous luster with white streak. The density of brandtite is 3.67 g/cm3 with a hardness of 3.5 – approximate to a copper penny.
Occurrence of Brandtite and Useful Mineral Association
Brandtite occurs in metamorphosed Fe–Mn orebody; and in a metamorphosed stratiform zinc orebody. It is often associated with minerals such as lead, sarkinite, flinkite, caryopilite, galena, barite, calcite, rhodochrosite, sphalerite, franklinite, willemite, chalcopyrite, and lollingite.
References