Keyite

Keyite


Composition: Cu2+3(Zn,Cu2+)4Cd2(AsO4)6(H2O)2
Crystal System : Monoclinic
Colours: Deep-blue
Lustre : Adamantine
Hardness (H) : 3.5-4.0
Year of Discovery: 1975
IMA Number: 1975-002
IMA Status: Approved
Discovered By: Charles Key (American dealer)
Named for: Discoverer
References: Embrey et al. (1977a)

Tsumeb is the Type Locality

Distribution

Very rare. Second oxidation zone, although the precise location for the type specimen is not known. 

It is probable that the type material came from 28 Level, where a 1975 discovery of schultenite with cuprian adamite was made (Von Bezing et al., 2014) and which material is now known to have yielded keyite. Gebhard (1999) notes that co-type material was recovered from 30 Level, also in the second oxidation zone.

Occurrence

  • Supergene
  • 2nd Oxidation Zone

Paragenetic and General Notes

Keyite was the first-described natural arsenate of cadmium.

Both acicular and equant crystal habits are observed, though not in combination.  Acicular crystals typically have a lower (vitreous) lustre, while the equant crystals are adamantine and gemmy. 

Despite its striking colour, keyite is easily overlooked because of its crystal size. Analysis of its most common associate on many specimens confirms zincolivenite (rather than cuprian adamite).