Iron Ore, Chromite and Steel-Making Minerals

Types of iron ore

Most of the world’s iron ore comes from banded iron formations, ancient layered rocks of iron oxide and silica, mostly well over two billion years old. Over time, weathering and groundwater leached out the silica in some of them and left high-grade hematite bodies. Those are the deposits behind the big direct-shipping mines of Western Australia’s Pilbara and Brazil’s Carajás. The main ore minerals are:

• Hematite, the most important ore by tonnage, which can often be shipped after only crushing and screening.
• Magnetite, which is magnetic and usually lower grade in the rock, so it’s ground and separated with magnets into a high-grade concentrate. Taconite, mined in Minnesota’s Iron Range, is a magnetite-bearing rock of this kind.
• Goethite and limonite, hydrated iron oxides that form part of many Australian ores.

Our article on Carajás iron ore describes one of the richest of these deposits, and Simandou in Guinea covers a high-grade deposit that needed a new railway and port to reach market.

Lump, fines, pellets and what grade means

Iron ore is sold as a product, and the product depends on size and processing. Lump is coarse ore that can go straight into a blast furnace. Fines are the smaller particles, which have to be sintered into a porous cake first. Pellets are made from finely ground concentrate rolled into balls and fired, and they give steelmakers a very consistent feed. Our guides to lump, fines and blue iron ore and pelletization go into each.

Grade is quoted as percent iron (Fe). Widely used price indices are based on fines at 62% Fe delivered to China, with premiums and discounts for higher or lower iron and for impurities such as silica, alumina and phosphorus. Direct reduction plants need especially pure pellets, often called DR-grade, which is why high-grade ore has become more valuable as steelmakers cut emissions. Impurities matter as much as iron content. Phosphorus makes steel brittle and alumina makes a blast furnace harder to run, so a clean ore can be worth more than a dirtier one with slightly more iron.

Two routes from ore to steel

The blast furnace route still makes most of the world’s steel, and it’s the reason metallurgical coal is mined alongside iron ore. Direct reduction, using natural gas or, in newer plants, hydrogen, with an electric arc furnace is the main route being developed to cut steel’s carbon emissions. Our article on extracting iron from iron ore covers both.

Where iron ore is mined and shipped

Iron ore is one of the largest bulk commodities by tonnage, and a few countries dominate the seaborne trade. Australia and Brazil are the biggest exporters, from the Pilbara and from Carajás and the Iron Quadrangle. China is by far the biggest buyer, and it also mines a lot of lower-grade ore of its own. Other important producers include Canada’s Labrador Trough, Sweden’s magnetite mines at Kiruna, South Africa, Ukraine and Russia, with new supply coming from West Africa. Reserves are a different question from output, and our page on iron ore reserves by country uses USGS figures to compare them. For the largest producers in one country, see Australian iron ore companies.

Chromite and stainless steel

Chromite, an oxide of chromium and iron, is the only commercial ore of chromium. Nearly all of it is smelted into ferrochrome, which goes into stainless steel. Stainless needs at least about 10.5% chromium to form the thin oxide layer that stops it rusting. South Africa’s Bushveld Complex holds most of the world’s chromite resources, and Kazakhstan, Turkey and Finland are other important producers. Chrome ore is priced off grade, usually quoted as percent Cr₂O₃, and the chromium-to-iron ratio, which is why there’s no single chromite price per ton. Nickel, manganese and molybdenum are the other main alloying metals in steel. Manganese is covered in our battery metals guide.

How iron ore and chromite are explored for

Iron oxides show distinctive absorption features in visible and near-infrared light, so iron-rich rocks and soils stand out in multispectral satellite imagery, and magnetite shows up strongly in magnetic surveys. Banded iron formations also form ridges that are easy to follow on terrain models. Chromite sits in ultramafic rocks, which can be mapped from their spectral signature and from magnetics. Iron ore and chrome are among the 23 minerals clients have commissioned from our satellite mineral detection service, which ranks Exploration Targets ahead of a JORC or NI 43-101 resource estimate, not as a replacement for drilling and estimation.