Although iron ore deposits were recorded in Western Australia as early as 1888, not until 1960 were the economic and political conditions conducive to assessment of their potential. Since that time, regional geologic mapping and intensive local evaluation have increased the total reserves from 275 to 24,000 million tons of ore containing 55% or more iron. This ore is of three main types: hematite enrichment, pisolitic limonite, and sedimentary ores. These contribute to production in the approximate porportions 20:2:1, whereas the equivalent proportions for reserves are 200:70:1.

Hematite enrichment ore formed by selective replacement by hematite, probably during Proterozoic time, of a banded iron-formation (BIF) host. Although such ore bodies are widespread in Archean (>2,500 m.y.) BIFs of the Yilgarn and Pilbara blocks, the largest ore bodies, exceeding 1 billion tons, are in the lower Proterozoic (c.2,000 m.y.) BIFs of the Hamersley iron province. Ore bodies of this type show stratigraphic and structural control. The ore is hematite with a variable admixture of late geothite. Pisolitic limonite ore, which forms sheets capping elongate sinuous mesas along rivers draining the Hamersley iron province, was formed during the Tertiary in the flat beds of a sluggish paleodrainage system which is closely paralleled by present drainage lines. Sedimentary iron ore is represented by concentrations of supposedly clastic hematite within folded Proterozoic (1,800 m.y.) sediments of the Yampi Sound area.

With a good overseas market available in Japan, export of ore commenced in 1966 and has risen rapidly to 73 million tons in 1973. In the earlier years of

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export, growth was rapid and profitable, but more recently has been affected adversely by reevaluation of currencies, industrial troubles, and developing competition for markets from Brazil, South Africa, and India.

The future will have to contend with the problems mentioned, also with the threat of a fuel crisis affecting shipping and, in the long term, the high phosphorus content of some of the ore. With huge reserves available, the demand for this iron ore will continue and some of the present problems will be solved.

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