Brockman Tiger eye mine (Marra Mamba), Mount Brockman, Ashburton Shire, Western Australia, Australiai

Regional Level Types
Brockman Tiger eye mine (Marra Mamba)	Mine
Mount Brockman	Mountain
Ashburton Shire	Shire
Western Australia	State
Australia	Country

Located approximately 50 kilometers northwest of Tom Price, near Mt. Brockman, adjacent to Caves Creek Valley on Hammersley Station.

The Marra Mamba Formation is an iron-rich sedimentary unit in the Archaean-Paleoproterozoic Hamersley Group (about 2.5 Ba) comprising chert, ferruginous chert, jaspilite, banded iron assemblages, minor shale, siltstone, and mudstone originating in a marine environment. It tends to be more friable, with a higher ochreous goethite content than the younger overlying Brockman Formation. The goethite results both from hydration of isolated iron oxide microlaminae and from weathering of the disseminated carbonates and silicates.
During explorations in 2000, it was found to have highly uniform stratigraphy over its provincial extent, even if diagenetic and weathering processes caused considerable alteration to the lithology. It comprises 3 units:
(1) The uppermost Mount Newman unit is about 55 m thick and consists of magnetite-rich associations, which include quartz, magnetite, minnesotaite, riebeckite, stilpnomelane, dolomite (or ankerite), calcite, and traces of pyrite.
(2) The McLeod member is similarly about 50 m thick, sulfide-rich, and contains variable amounts of quartz, siderite, dolomite (or ankerite), stilpnomelane, minnesotaite, pyrrhotite and/or pyrite, and small amounts of carbon.
(3) The lowest 140 m Nammuldi unit has little economic interest and therefore has not received much attention.
The banded iron-formation assemblages, at very low temperatures of metamorphism, do not appear to be as sensitive to relatively small temperature changes as do very low-grade metamorphic volcanics. The iron-formation assemblages may have originated over a temperature range of 100-300°C.

A number of deposits for Tiger Eye are found here, mined by Western Australian specimen dealers, and the material is well known overseas. Probably most of the specimens of tiger eye sold internationally come from here. (Specimens labelled Perenjori are more likely to have come from Marra Mamba). Specimens may also be labelled Mount Brockman or Brockman.

Information about the history of the deposit is in short supply, and it appears to have always been in recent times the preserve of local specimen miners as small operations. In 2005, David Vaughan discovered one of the largest tiger eye specimens ever at Marra Mamba. It was placed on display at the Tucson Show and later cut into slabs. One is said to form the countertop of a hotel reception area at Port Hedland. Another, the size of a large dining room table, is on display at the Kalgoorlie Miners Hall of Fame.

Tiger eye is a golden-brown, chatoyant, siliceous fiber vein, rich in quartz and iron oxides, usually with some riebeckite. It contains multiple bands of green, red, blue, and orange jasper with golden tiger eye, which has a chatoyant effect with a golden sheen reflected from the fine parallel fibers in the slabs.

Originally it was thought to be a pseudomorph of crocidolite formed by the silica replacement of crocidolite (riebeckite) fibers. Another more recent theory suggests the veins formed as fibrous quartz crystals with interspersed hematite and riebeckite fibers, growing rapidly from the surrounding rocks during low-grade metamorphism.

While tiger eye is the most common name, a confusing variety of other names are applied to related material. Hawks eye (blue), falcons eye (green), and pietersite (brecciated) are a few. "Bull's eye" is a heat-treated Tiger eye, where the yellow limonite has been converted to red hematite, giving it an overall red color.

Please be aware that 'Tiger Iron,' which is the thin-banded hematite, jasper, and golden tiger eye material, may come from the Ord Ranges in the Port Hedland Shire. Material that is largely 'Tiger Eye' is more likely from the site you are reading this on. Both are shown as pictures under this site, and the material can be compared.

Other Regions, Features and Areas containing this locality

References