May 20 2014
Chalcoalumite was named after the essential elements, copper (Greek term ‘chalkos’) and aluminum sulfate (Latin term ‘alum’), in the composition.
Properties of Chalcoalumite
The following are the key properties of chalcoalumite:
- Cell Data
- Space group: P21
- a = 17.090
- b = 8.915
- c = 10.221
- β = 95°53’
- Z = 4
- Crystal Data
- Monoclinic
- Point group: 2
- As thin tabular enantiomorphous crystals with {100} exhibiting an equilateral triangular outline, to 0.5mm
- As spherical crystal aggregates
- Most commonly as fibrous to massive botryoidal crusts
- Twinning: Typically twinned on {100} yielding composites that closely resemble thick untwinned individuals. Twinning on {010} forms diamond-shaped tablets. Twinning on {136} produces a swallowtail composite with deep reentrant, or fourlings and eightlings. Diamond-shaped eightlings combining all three twin laws have been noted
- X-ray powder pattern: 8.502 (100), 4.250 (91), 4.178 (23), 7.898 (22), 4.786 (22), 5.100 (13), 2.520 (11)
- Chemical Composition
| Elements |
Content 1 |
Content 2 |
| Al2O3 |
38.88 |
38.80 |
| H2O |
30.60 |
30.84 |
| SO3 |
14.67 |
15.23 |
| CuO |
14.56 |
15.13 |
| insol. |
0.28 |
| Total |
98.99 |
100.00 |
- Optical Properties
- Optical class: Biaxial (+)
- Pleochroism: Weak, X = pale green; Y = colorless; Z = robin’s egg-blue
- Orientation: Y = b; Z ^ c = 22°
- Dispersion: r < v, strong
- α = 1.523; β = 1.525; γ = 1.532
- 2V(meas.) = Small
- Estimated Properties
| Electron density |
Bulk density (electron density) = 2.29 g/cm3
note: Specific gravity of chalcoalumite = 2.25 g/cm3 |
| Photoelectric |
PEChalcoalumite = 6.07 barns/electron
U=PEChalcoalumite x ρ electron density = 13.87 barns/cm3 |
| Fermion index |
Fermion index = 0.0007402576
Boson index = 0.9992597424 |
Radioactivity
|
Chalcoalumite is not radioactive
|
How to Identify Chalcoalumite
Chalcoalumite can be identified in the field by its color variations, such as blue, blue-gray, greenish-blue, and light blue-green. Its transparent to translucent form has {100} perfect cleavage. This mineral has a vitreous - dull luster with bluish-white streak. The fracture on this mineral is flexible.
The density of chalcoalumite is 2.29 g/cm3 with a hardness of 2.5 – approximate to finger nail. It is non-fluorescent.
Global Distribution
Chalcoalumite is distributed in the following places:
- USA - From Bisbee, Cochise Co. and in the Grandview mine, Grand Canyon, Coconino Co. Arizona; at the Titusville mine, head of Kendall Gulch, San Juan Co. Colorado; and in the Lovelock mine, Table Mountain district, Churchill Co. Nevada
- Canada - On the Spatsum claim, south of Ashcroft Manor, British Columbia
- Wales - From the Britannia mine, Snowdonia, Gwynedd
- England - At South Wheal Crebor, Tavistock, Devon, and in the Penberthy Croft mine, St. Hilary, Cornwall
- Belgium - At Ottre, near Salmchateau
- Slovakia - From Lubietova, near Banska Bystrica (Libethen, near Neusohl)
- Italy - At the Baccu Locci mine, near Villaputzu, Sarrabus district, Sardinia
- Sweden - From the Sjo mine, near Grythyttan, Orebro
- South Africa - In the Mbobo Mkulu Cave, near Ngodwana, Eastern Transvaal
Occurrence of Chalcoalumite and Useful Mineral Association
Chalcoalumite occurs in a rare secondary mineral in the oxidized portions of copper deposits. It is often associated with minerals such as cuprite, malachite, azurite, goethite, mbobomkulite, and hydrombobomkulite.
References