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Formula: Al2(SO4)(OH)3Cl.6H2O
Hydrated sulphate
Crystal System: Monoclinic
Specific gravity: 1.97 measured, 1.974 calculated for the empirical formula
Hardness: 2 to 2½
Streak: White
Colour: Colourless
Solubility: Insoluble in water, dissolves slowly in warm 20% hydrochloric acid
Environments
Volcanic igneous environments
Hydrothermal environments
Vendidaite was approved in 2012 and to date (October 2024) has been reported only from the type
locality.
Localities
At the type locality, La Vendida Mine, Sierra Gorda, Antofagasta Province, Antofagasta, Chile, the copper
sulphide mineralisation is associated with dacitic
andesitic volcanic
breccias. The
supergene mineralisation is represented mainly by sulphates,
chlorides and clay minerals.
Specimens with vendidaite were collected in La Vendida open pit. The holotype material originates from a
2 × 1 × 1 m3 block at the edge of the quarry. Subsequently vendidaite was found on the mine dumps.
Associated minerals are intermediate members of the
aubertite-magnesioaubertite
solid-solution series, belloite,
eriochalcite, alunite,
kaolinite and halloysite.
Belloite (formed as a product of alteration of
eriochalcite) and vendidaite are the latest minerals in this
association.
Sulphate minerals (mainly alunite and
jarosite) are abundant in the quarry. Associations of copper sulphates and
chlorides (like that bearing vendidaite) are located in small areas from 1 to 5 m across where
secondary minerals occur in thin fissures. The host rocks
(dacitic
andesitic volcanic
breccias) are strongly altered.
Vendidaite forms colorless transparent, vitreous, platy crystals up to 0.01 × 0.3 × 0.3 mm3 in
size, forming clusters up to 0.5 mm across, as well as white, fine-grained aggregates
(CM 51.4.559-568).
Vendidaite from La Vendida Mine - Image
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