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Formula: NaCu2(SO4)2(OH).H2O
Hydrated sulphate containing hydroxyl, tsumcorite group
Crystal System: Monoclinic
Specific gravity: 3.47 to 3.51 measured, 3.54 calculated
Hardness: 4½
Streak: Greenish white
Colour: Bright green; green in transmitted light
Solubility: Slowly soluble in water, readily soluble in acids
Environments
Natrochalcite is a rare secondary mineral typically
formed in arid climates in the oxidised zone of copper deposits
(HOM).
Localities
At the Lomas Bayas Mine, Sierra Gorda, Antofagasta Province, Antofagasta, Chile,
secondary minerals in the
porphyry copper deposit include
anhydrite, jarosite,
mendozavilite-NaFe, natrochalcite,
sampleite and strengite
(MM 76.5.1175–1207).
At the type locality, the Chuquicamata mine, Chuquicamata District, Calama, El Loa Province, Antofagasta, Chile,
natrochalcite forms single crystals and fibrous or acicular aggregates to 4 cm, and solid crusts to 2 cm thick
in the oxidation zone of the copper deposit; the climate is arid
(Mindat).
Associated minerals include kröhnkite,
antlerite, brochantite,
chalcanthite, blödite,
atacamite and gypsum
(HOM).
At the Cape Calamita Mine, Capoliveri, Livorno Province, Tuscany, Italy, natrochalcite is associated with
kröhnkite and brochantite
(HOM).
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