Aug 15 2013
Auriacusite was named after the Latin word ‘auri’ meaning (golden yellow and ‘acus’ meaning (needle, in allusion to its color and habit). This mineral belongs to the olivenite group.
Properties of Auriacusite
The following are the key properties of auriacusite:
- Cell Data
- Space group: Pnnm
- a = 8.6235(7)
- b = 8.2757(7)
- c = 5.9501(5)
- Z = 4.
- Crystal Data
- Othorhombic
- Point group: 2/m2/m2/m
- As acicular needles, elongated on [001], to 0.1 mm
- In fibrous mats
- X-ray powder pattern: 4.884 (100), 2.991 (92), 2.476 (85), 2.416 (83), 2.669 (74), 4.218 (69), 1.582 (54).
- Chemical Composition
| Elements |
Content 1 |
Content 2 |
| Fe2O3 |
31.36 |
29.11 |
| CuO |
19.93 |
29.00 |
| As2O5 |
17.32 |
41.89 |
| Sb2O5 |
12.71 |
- |
| ZnO |
0.80 |
- |
| SiO2 |
0.76 |
- |
| TeO3 |
0.53 |
- |
| SO3 |
0.50 |
- |
| PbO |
0.16 |
- |
| P2O5 |
0.04 |
- |
| SeO3 |
0.04 |
- |
| Cl |
0.04 |
- |
| Ag2O |
0.03 |
- |
| -O=Cl |
0.01 |
- |
| Total |
84.21 |
100.00 |
- Optical Properties
- Optical class: Biaxial (+)
- Orientation: X = a; Y = c; Z = b
- Dispersion: strong, r < v, probable
- α = 1.830(5); β = 1.865(5); γ = 1.910(5)
- 2V(meas.) = 83.3(3)°
- 2V(calc.) = 84.6°
How to Identify Auriacusite
Auriacusite can be identified in the field by its ochreous yellow color. Its transparent form has a silky luster with brownish yellow streak. The fracture on this mineral is uneven. The density of auriacusite is 4.447 g/cm3 with a hardness of 3 Mohs.
Global Distribution
Auriacusite is distributed mainly in the Black Pine mine, 14.5 km NW of Philipsburg, Granite County, Montana, USA.
Occurrence of Auriacusite and Useful Mineral Association
Auriacusite occurs in a secondary mineral in the weathering zone of a polymetallic sulfarsenide deposit. It is often associated with minerals such segnitite, pyrite brochantite, malachite, and tetrahedrite.
References