Chalcanthite
Chalcanthite is a water-soluble copper sulphate mineral that forms beautiful blue fibrous crystals. It is the copper analog of Melanterite. Chalcanthite is a hydrated copper sulphate mineral formed after the decomposition of other copper minerals due to the action of surface waters. It is often found in mines as a post-mining formation on mine walls as encrustations or stalactites.
Natural gem-quality crystals are quite rare so gems are mostly faceted from lab-grown material. These gems have one of the most intense, saturated bright blue colors availble for gems. Care must be taken to store gems or specimens in a sealed container with a desiccant to keep them dry since Chalcanthite can slowly absorb moisture from the air then lose it again. Over time, this cycle can cause a beautiful gem or mineral specimen to be reduced to a pile of blue dust.
Deposits of Chalcanthite are widespread; commercial deposits may occur in arid regions. From the Island of Cyprus. On Vesuvius, Campania, Italy. From Rammelsberg and Goslar, Harz Mountains, Germany. Abundant at Rio Tinto, Huelva, Spain. In Chile, from Chuquicamata, at Quetena, near Calama, and Copaquire, Antofagasta. In the USA, in Arizona, at the United Verde mine, Yavapai County, and in the Clifton-Morenci district, Greenlee County; from the Blue Bird mine, Fierro-Hanover district, Grant County, New Mexico; commercial amounts in the Bluestone mine, Yerington district, Lyon County, Nevada; at Butte, Silver Bow County, Montana; from Ducktown, Polk County, Tennessee.
| Chemical Formula: | CuSO4 · 5H2O |
| Hydrated Copper Sulfate | |
| Molecular Weight: | 249.69 gm |
| Composition: | Copper | 25.45 % | Cu | 31.86 % | CuO |
| Hydrogen | 4.04 % | H | 36.08 % | H2O | |
| Sulfur | 12.84 % | S | 32.07 % | SO3 | |
| Oxygen | 57.67 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE | |||
| Crystallography: | Triclinic – Pinacoidal |
| Crystal Habit: | Crystal short prismatic {001} or less commonly tabular {111}. Natural crystals rather rare. Commonly found as stalactic material, massive, granular filling veins (cross-fiber veinlets) and as crusts. |
| Twinning: | Rarely as cruciform intergrowths with {010} common between individuals |
| Cleavage: | Imperfect on {110}, Indistinct on {111}; and, {110} in traces |
| Fracture: | Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 2.5 |
| Density: | 2.286 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Other: | Soluble in water, dehydrates in dry air. |
| Health Warning: | CAUTION: Poisonous! Copper sulfate solutions are poisonous. Do not lick or ingest. Do not touch with bare hands or wash hands immediately after handling! |
| Color: | Green, Green Blue, light Blue, or dark Blue; Colorless to pale Blue in transmitted light |
| Transparency: | Translucent to Transparent |
| Luster: | Vitreous to Resinous |
| Refractive Index: | 1.516 – 1.546 Biaxial ( – ) |
| Birefringence: | 0.0300 |
| Dispersion: | r < v |
| Pleochroism: | None |
| Color: | Green, Green Blue, light Blue, or dark Blue; Colorless to pale Blue in transmitted light |
| Transparency: | Translucent to Transparent |
| Luster: | Vitreous to Resinous |
| Refractive Index: | 1.516 – 1.546 Biaxial ( – ) |
| Birefringence: | 0.0300 |
| Dispersion: | r < v |
| Pleochroism: | None |
