Iron is the most commonly used metal in the world, accounting for 95% of all metals used each year. Iron ore is the rock and mineral from which iron can be smelted economically.
Iron ore is vital to the iron and steel industries. Almost all (98%) iron ore is mined to produce iron and steel objects we use - from paper clips, furniture, and cars, to steel beams for buildings.
Huge demand for iron ore
Every year, 2 billion tons of raw iron ores are produced. Currently, 50 countries are mining iron ores. Australia and Brazil dominate the iron ore exports (72% of the market).
The world's largest producer of iron ore is Brazil's Vale, followed by Australia's Rio Tinto and BHP.
World consumption of iron ore grows 10% per annum on average. Among them, China is the largest consumer of iron ore, which translates to be the largest steel producer.
Iron ore prices rebounded sharply in 2022. It currently rises towards $160/t. But an Australian government report put that iron ore prices will weaken over the short-to-medium term: it will be $110/t in 2022, then $80/t next year, and reach $55/t by 2027.
4 types of iron ore
The most important iron ore is found in sedimentary rocks.
There are more than 300 kinds of iron-bearing minerals, but only 20 kinds are used as raw iron ores. The most important 4 types of iron ores are magnetic ore, hematite, limonite, and siderite.
1. Magnetite - the best iron ore
Magnetite, also called lodestone. It is a natural magnet, hence the name, giving it a distinguishing characteristic.
Magnetite is the best iron ore. It has the highest iron content (up to 72.4%) and the strongest magnetic power. It can be separate from gangue, producing a high-grade concentrate (above 70%) with very few impurities.
- Magnetite formula: Fe3O4
- Iron content: Up to 72.4%
- Magnetite color: Black
- Magnetite hardness: 5.5-6.5
- Magnetite luster: Metallic
- Features: The best iron ore, strongest magnetic ore
- Imaginary hematite and semi-artificial hematite: Magnetite oxidizes to hematite, but retains the crystalline form of magnetite.
- Titanium magnetite: Magnetite containing titanium (TiO2) oxide
- Vanadium magnetite: Magnetite containing vanadium (V2O5) oxides
- Vanadium-titanium magnetite: magnetite containing titanium and vanadium oxides
- Pyrrhotite: Symbiotic with pyrite (FeS). It is the second most common magnetic mineral.
Magnetite is rich in reserves. Australia, Brazil, America's Minnesota and Michigan, eastern Canada, and northern Sweden are the largest producers.
Magnetite's greatest use is as a high-quality iron ore for steel manufacture. It can also be applied in paints, ceramics, etc.
2. Hematite - the most important iron ore
Hematite, also spelled haematite, its name is derived from the Greek word for “blood,” in allusion to its red color.
Hematite is the most important industrial iron ore in terms of the quantity used, but has a slightly lower iron content than magnetite. It often coexists with magnetite and limonite and is easier to restore than magnetite.
- Hematite formula: Fe2O3
- Iron content: Slightly lower than magnetite (up to 69.9%)
- Hematite color: Red, light gray, black
- Hematite crystal: Trigonal system
- Hematite hardness: 5.5-6.5
- Feature: The most important iron ore
Hematite is produced in Australia, Brazil, India, and other countries. Raw hematite beneficiation is generally magnetic separation, flotation, gravity separation, etc. But sometimes it occurs in higher-grade deposits, called direct-shipping ore (DSO). Such hematite can be extracted with simple crushing and screening.
Hematite has wide use, but its economic significance is very small compared to the importance of iron ore. It produces pigments, jewelry, healing stone, etc.
3. Limonite - inferior iron ore
Limonite is named from the Greek for meadow, from occurrences in bogs.
Limonite is not a true mineral but a mixture of hydrated iron oxide minerals mostly made up of goethite. It occurs as a secondary material, formed from the weathering of other iron ores or deposited as bog, lake, and shallow marine sediments.
- Limonite chemical formula: FeO(OH)·n(H2O)
- Iron content: Up to 59.8%
- Color: Yellowish (tan, dark brown, black gray)
- Limonite luster: Earthy
- Limonite hardness: 4-5.5
- Features：Amorphous and variable iron oxide, large water content
Most of limonite exists in the form of 2Fe2O3•3H2O. According to different crystal water content, limonite minerals can be divided into water hematite, needle hematite, limonite and the like.
It has been used as low-quality iron ore for thousands of years due to the small deposit and large water content. Therefore, limonite needs to be briquetted before smelting. It is also the most important ocher and umber pigment.
4. Siderite - carbonate of iron with no magneticity
Siderite is also the name of a type of iron meteorite. It takes its name from the Greek word sideros, meaning "iron".
Siderite is a hard and dense carbonate of iron, containing no sulfur or phosphorus and is mixed with carbonates such as magnesium, manganese, and calcium. Siderite is roughly the equivalent of calcite but with iron replacing the calcium.
- Siderite formula: FeCO3
- Iron content: Up to 48.2%
- Siderite color: Gray, Yellow-brown
- Siderite hardness: 3.75-4.25
- Siderite luster: Vitreous, silky, pearly
- Features: Non-magnetic, easily weathered into limonite
Siderite occurs mostly in sedimentary and hydrothermal environments or in igneous pegmatites (a variety of granite occurring in veins). Other minerals associated with siderite include barite, fluorite, galena, quartz, dolomite, sphalerite, pyrite, etc.
Although siderite is not high in iron content, the iron content of the CO2, after calcination, increases significantly due to the liberation, and the ore becomes porous with good reduction. Except for producing steel, siderite is the most permanent earth pigment for artists.