Minerals

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General Information

Chalcanthite

Chalcanthite is the mineral form of coppersulfate. Because synthetic coppersulfate crystals are much brighter than the natural ones (but a lot cheaper), they are ocasionally sold as real minerals. This kind of fraud happens a lot, people tend to call their synthetic coppersulfate crystals chalcanthite, even if its not the real mineral. If you look at photo 1 and 2, you can see the different between the two types of crystals. Chalcanthite is an instable mineral and after a time starts to disintegrate (just like coppersulfate). Partially due to humidity, but also due to the water that is bound in its crystal structure. It tends to move around in the matrix, destroying the crystal structe, making it dull looking and eventually it will start crumbling. It is impossible to keep a piece of chalcanthite in a perfect condition even if blocked from any moist in the air.[1]

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Chemical & Physical Information

Trivial NameChalcanthite
Chemical NameCoppersulfate Pentahydrate
Chemical FormulaCuSO4, 5H2O
Density2,12-2,3 g·cm-3
Molar mass?
Hardness2,5
Crytal systemTriclinic
Unit cell?
Crystal habitStalactites, crusts, rarely as natural crystals.
FractureConchoidal
CleavageImperfect [110], unclear [111]
ColourBleu Green
LusterGlass
StreakWhite
OpacityTranslucent to transparent
SafetyPoisonous
ExtraHygroscopic
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Photos

Chalcanthite

(7 cm)

Chalcanthite

(16 cm)

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Sources

[1] Wikipedia

[2] Specimen from my personal collection, photo taken by me.