May 28 2014
Perroudite has an orthorhombic crystal system. It was first discovered in Cap-Garonne in Var, France in 1992.
It was named for Pierre Perroud, Professor at Voltaire College in Geneva, Switzerland, for his work on Cap Garonne mine minerals.
Properties of Perroudite
The following are the key properties of Perroudite:
- Cell Data
- Space Group: P21212
- a = 17.43(2)
- b = 12.24(2)
- c = 4.35(1)
- Z = 2
- Crystal Data
- Orthorhombic
- Point Group: 2/m 2/m 2/m
- Fibrous tufted aggregates of crystals, to 0.07mm, prismatic on [001], flattened on {100}, which may have hollow terminations
- Twinning: Observed as contact twins on {0hl} [sic]
- X-ray Powder Pattern: 3.012 (100), 2.965 (80), 3.945 (60), 2.638 (35), 3.694 (30), 2.740 (30), 2.446 (30)
- Chemical Composition
| Elements |
Content 1 |
Content 2 |
Content 3 |
| Hg |
53.08 |
51.95 |
57.68 |
| Ag |
22.86 |
23.54 |
19.43 |
| I |
10.32 |
10.80 |
6.45 |
| S |
6.67 |
9.07 |
8.79 |
| Br |
3.67 |
0.96 |
2.11 |
| Cl |
2.89 |
2.83 |
3.56 |
| Total |
99.49 |
99.15 |
98.02 |
- Optical Properties
- Optical Class: Biaxial (+)
- Pleochroism: Very intense
- X = dark brownish-red
- Y = yellow
- Z = brownish-yellow
- Orientation: X = c; Y = b; Z = a
- Dispersion: r > v, very strong
- α = 2.3
- β = 2.4
- γ = n.d
- 2V(meas.) = ∼70°
- R1–R2: n.d
- Estimated Properties
| Electron density |
Bulk density (electron density) = 5.90 g/cm3
note: Specific gravity of Perroudite = 7.03 g/cm3 |
| Photoelectric |
PEPerroudite = 1001.26 barns/electron
U = PEPerroudite x ρElectron density = 5911.61 barns/cm3 |
| Fermion index |
Fermion index = 0.16
Boson index = 0.84 |
Radioactivity
|
Perroudite is not radioactive
|
How to Identify Perroudite
Perroudite can be identified from its light red color, orange red streak, vitreous luster, and perfect cleavage. It is transparent in nature, and its fractures are irregular. It can be formed into needle-like crystals, prismatic crystals, or aggregates.
The relative hardness of perroudite is 2.
Global Distribution
Perroudite is distributed in the following places:
- Cap Garonne mine, near le Pradet, Var, France
- Schone Aussicht mine, near Dernbach, North Rhine-Westphalia, Germany
- Broken Hill, New South Wales, Australia
- Coppin Pool, Pilbara district, Australia
- Anticline prospect, 11km west-south-west of Ashburton Downs homestead, Capricorn Range, Western Australia
Occurrence of Perroudite and Useful Mineral Associations
Perroudite occurs as an alteration of tennantite in conglomerates and sandstones. It can also be found in a quartz vein carrying oxidized galena.
Cinnabar, pyromorphite, covellite, phosgenite, cerussite, anglesite, kaolinite, gold, and iodargyrite, as well as mercurian and argentian tennantite are some of the minerals that are closely associated with perroudite.
References