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Formula: NaNi4(CO3)3)(OH)3).3H2O
Hydrated carbonate, nickel-bearing mineral
Crystal System: Hexagonal
Specific gravity: 3.18 measured, 3.193 calculated
Hardness: 3
Streak: Pale green
Colour: Emerald-green, bright grass-green
Solubility: Not readily soluble in cold 1:1 hydrochloric acid or 1:1 nitric acid
Environments
Localities
At the 132 North Ni Mine, Widgiemooltha, Coolgardie Shire, Western Australia, kambaldaite occurs as apple-green
crystals on olive-green globules of gaspéite
(Mindat photo).
Kambaldaite from Widgiemooltha - Image
At the type locality, the Otter Shoot Nickel Mine, Juan complex, Kambalda Nickel mines, Kambalda, Coolgardie Shire,
Western Australia, the primary sulphides, which occur as
assemblages of pentlandite -
pyrrhotite - pyrite and
pentlandite - millerite -
pyrite, have been altered to
supergene assemblages consisting largely of
violarite and pyrite, which have
decomposed on further oxidation to a goethitic residue in which the
secondary nickel minerals
have been deposited.
The samples in which the kambaldaite was found are from a depth of about 20 meters, and consist largely of
goethite with some reevesite and
residual pyrite. The kambaldaite, together with
gaspéite and some aragonite, occurs
on fracture surfaces in the goethite in a variety of types: massive,
crystalline, nodular and chalky. The massive kambaldaite occurs as cryptocrystalline veins, layers and
concretionary growths up to about 2 mm thick, commonly intergrown with
gaspéite. The crystalline kambaldaite occurs as encrustations on the
more massive kambaldaite and on gaspéite. The encrustations are bright
grass-green to emerald-green in colour, and generally consist of tiny hexagonal prisms. The nodular kambaldaite
occurs as partial spheres about 1 mm in diameter. Some of the nodules are very glossy and have a rich emerald-green
colour; when these spheres are broken, they are seen to consist of radiating hexagonal prisms. The chalky
kambaldaite consists of pale green pulverulent (powdery or crumbly) material which, at high magnifications, is
seen to consist of masses of very fine acicular crytals.
The mineral occurs near the base of the oxide zone in the
supergene weathering profile, where the activity of
nickel species in solution is particularly high due to the dissolution of
violarite. Carbonate and sodium activities must also have been high for
kambaldaite to form.
Although there are no appreciable amounts of sodium minerals in the
primary rock, the groundwater in the region is very saline. This
high sodium content is probably due to seepage from salt lakes in the vicinity. It therefore seems likely that
kambaldaite owes its origin to an unusual combination of elements in the groundwater. Significantly, the only
other secondary
sodium-nickel mineral found to date (in 1983), namely
nickelblödite, was also found at Kambalda
(AM 70.419-422).
Kambaldaite from Otter Shoot - Image
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