Sep 26 2013
Bearthite is a mineral containing phosphorus, oxygen, hydrogen, calcium and oxygen and belongs to the brackebuschite group of minerals. The mineral was first found on the western ridge of the Stockhorn, Zermatt Valley, Valais, Switzerland in 1993. It was named after Professor Peter Bearth for his pioneering petrologic studies of the high-pressure terranes of the western Alps.
Properties of Bearsite
The following are the key properties of Bearthite:
- Cell Data
- Space Group: P21/m
- a = 7.231(3)
- b = 5.734(2)
- c = 8.263(4)
- β = 112.57(8)°
- Z = 2
- Crystal Data
- Monoclinic
- Point Group: 2/m
- Rarely as aggregates of partly euhedral, flat prismatic crystals, to 1 mm; typically as smaller, usually corroded, anhedral grains
- X-ray Powder Pattern: 3.05 (100), 2.867 (61), 2.568 (39), 2.754 (27), 4.58 (22), 2.634 (21), 2.444 (19)
- Chemical Composition
| Elements |
Content 1 |
Content 2 |
Content 3 |
| P2O5 |
44.32 |
41.64 |
45.19 |
| SiO2 |
0.3 |
0.26 |
- |
| Al2O3 |
15.91 |
13 |
16.23 |
| La2O3 |
0.03 |
1.52 |
- |
| Ce2O3 |
0.04 |
3.15 |
- |
| Nd2O3 |
- |
0.82 |
- |
| FeO |
0.03 |
0.19 |
- |
| MgO |
0.12 |
1.64 |
- |
| CaO |
33.04 |
29.32 |
35.71 |
| SrO |
3.53 |
2.3 |
- |
| F |
0.48 |
0.6 |
- |
| Cl |
0.02 |
- |
- |
| H2O |
- |
- |
2.87 |
| -O = (F, Cl)2 |
0.2 |
0.25 |
- |
| Total |
97.62 |
94.19 |
100 |
- Optical Properties
- Optical Class: Biaxial (+)
- Orientation: X = b
- Dispersion: r < v, distinct
- α = 1.660–1.662
- β = 1.671–1.672
- γ = 1.690–1.696
- 2V(meas.) = 64°–65°
- Estimated Properties
| Electron density |
Bulk density (electron density)=6.55 g/cm3
note: Specific gravity of Bearthite =6.59 g/cm3 |
| Photoelectric |
PEBearthite = 4.34 barns/electron
U= PEBearthite x ρ Electron density= 28.39 barns/cm3 |
| Fermion index |
Fermion index = 0.0005
Boson index = 0.99 |
| Radioactivity |
Bearthite is not radioactive |
Global Distribution
Bearthite is distributed in the following places:
- Western ridge of the Stockhorn, Zermatt Valley, Valais, Switzerland
- Dora Maira massif, between the Po and Varaita Valleys, Piedmont, and around Passo di Vizze, Alto Adige, Italy
- Hollkogel, 12 km south-southwest of Murzzuschlag, Styria, Austria
- Vastana mine, near Nasum, Skane, Sweden
Occurrence of Bearthite and Useful Mineral Association
Bearthite occurs as an accessory mineral in high-pressure metamorphic rocks and in synmetamorphic quartz segregations.
It is closely associated with talc, albite, quartz, hydroxylherderite, goyazite, wardite, augelite, rutile, almandine, muscovite, paragonite, pyrope, coesite, kyanite, apatite and lazulite.
References