Aurichalcite | |
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General | |
Category | Carbonate mineral |
Formula (repeating unit) | (Zn,Cu)5[(OH)3|CO3]2 |
IMA symbol | Ach[1] |
Strunz classification | 5.BA.15 |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) (same H-M symbol) |
Space group | P21/m |
Unit cell | a = 13.82, b = 6.419 c = 5.29 [Å] β = 101.04°; Z = 2 |
Identification | |
Color | Pale green, greenish blue, light blue; colorless to pale blue, pale green in transmitted light |
Crystal habit | Typically in tufted divergent sprays or spherical aggregates, may be in thick crusts; rarely columnar, laminated or granular |
Twinning | Observed in X-ray patterns |
Cleavage | {010} and {100} Perfect |
Fracture | Uneven |
Mohs scale hardness | 2 |
Luster | Pearly, silky |
Streak | Light blue |
Diaphaneity | Transparent |
Specific gravity | 3.96 |
Optical properties | Biaxial (−) |
Refractive index | nα = 1.655 nβ = 1.740 nγ = 1.744 |
Birefringence | 0.0890 |
Pleochroism | Weak colorless to pale green |
2V angle | Measured: 1° to 4°, Calculated: 22° |
References | [2][3][4] |
Aurichalcite is a carbonate mineral, usually found as a secondary mineral in copper and zinc deposits. Its chemical formula is (Zn,Cu)5(CO3)2(OH)6. The zinc to copper ratio is about 5:4.[3] Copper (Cu2+) gives aurichalcite its green-blue colors.[5]
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