Otter Shoot Nickel Mine, Juan complex, Kambalda Nickel mines, Kambalda, Coolgardie Shire, Western Australia, Australiai

Regional Level Types
Otter Shoot Nickel Mine	Mine
Juan complex	Complex
Kambalda Nickel mines	Group of Mines
Kambalda	Town
Coolgardie Shire	Shire
Western Australia	State
Australia	Country

[Possibly identical to Otter-Juan mine.]
Otter shoot is southwest of the Juan shoots


Rare nickel secondary species from Kambalda invariably come from the Otter Shoot Mine, which was its name when operated by Western Mining Corporation. It is now named the Otter Juan Mine. Specimens appear to have been extracted from the oxidised zone in the early 1980's when an interest was taken in the rare species it contains, in particular Kambaldaite.

It is one of the older nickel mines in the area, operated by Western Mining Corporation between 1968 to 1999. Between 1998 to 2001, Western Mining exited the nickel mines around Kambalda. The Otter Shoot Mine was purchased by GBF Mining Pty Ltd in 2001, and later that year re-opened the mine. In 2007, Mincor Resources purchased the mine, and this company now owns and operates all the nickel mines on the Kambalda Dome. The ore is processed in BHP Billiton's nickel concentrator at Kambalda. Mincor sells the nickel concentrate also to this company as part of its processing deal.

The Otter Juan Complex has over 60 ore shoots on the northern boundary of the Kambalda Dome. It is considered the largest and richest deposit in the Dome. As is typical of all the deposits, the shoots lie on the Lunnon Basalt. The main ore shoot is called Edwards. This layer of massive ore contains 80-100% sulphides at 10-17% Ni to 0.8m above the basalt. Above this is a 1.2m thick layer of matrix ore at 40-80% sulphide and 2.5-7% Ni. In turn above this is disseminated ore 10-40% sulphides and 0.5-2.5 Ni. The hanging wall is talc-magnetite-chlorite ultramafic rock.

Interest in the rare secondary nickel species of the oxidised zone, started when R Harrison collected some material from the Number 1 ventilation shaft at the mine. This was shown to Western Australian collector and specimen miner, David Vaughan, who approached the CSIRO. The appropriately named Ernest Nickel identified the new species Kambaldaite from this material. The species is unique in composition, structure and has no close relatives.

The primary and supergene sulphides are pentlandite-pyrrhotite-pyrite, and pentlandite-millerite-pyrite, altered in the supergene zone to violarite and pyrite. This decomposes further by oxidation to a goethitic residue in which most of the secondary nickel species are deposited. The material is found around 20m below the surface, at the base of the oxidised zone, in a supergene weathering area. Kambaldaite,gaspeite,reevesite and some aragonite are found on fracture surfaces in the goethite. Important elements in the development of these rare species in this zone is the dissolution of violarite, high sodium content from saline seepage from nearby salt lakes, and the dissolution of carbonates from the wall rock and ore.

Most of the nickel deposits listed under Kambalda on Mindat occur within a few kilometres of each other, directly north of the East Kambalda townsite. Otter Shoot/Juan is the most northerly and the shoots of this complex in total trend north-west to south-east over a length of about 4 kilometres. Measured from the centre of the Otter Shoots are Durkin 1 kilometre south-east, Gellaty 1 kilometre south-west, McMahons 2 kilometres south-west, Ken 3 kilometres south-west, Coronet/McCloy 2 kilometres south, Long and Victor 5 Kilometres south-east and Lunnon 8 kilometres south south-east.

Otter Shoot is the type locality for hydrohonessite. This bright yellow species was found in 1978 in the wall of stope 103, 43 metres below the surface. The amount collected was too small for it to be identified, until several years later when more was found on the mine's dump. At Otter Shoot it forms surface encrustations of tiny hexagonal crystals on botryoidal quartz and magnesite in a fracture in supergene Ni-Fe sulphides violarite and pyrite. The species here was found as tiny hexagonal flakes and to be intimately associated with silica, and was disseminated in a mass of the secondary minerals gaspeite, pecoraite, and some coarse gypsum crystals and minor goethite. Better specimens of hydrohonessite were to be later uncovered at 132 North mine near Widgiemooltha.

Other Regions, Features and Areas containing this locality

References