There are several types of iron ore. The most commonly mined type is Hematite, particularly in Brazil, China and Australia, where it makes up 96% of all exports. The ore itself is a deep, brownish red colour which is where the name comes from (Haima is the Greek word for blood) and has a chemical formula of Fe2O3 and is also known as Ferric Oxide. Hematite has a very high iron content, which can makes up about 70% of the ore but it can also contain quite a substantial amount of penalty elements such as Phosphorous, Aluminium and Water. These high grade ores are also known as direct shipping ores because they are mined and extracted with a simple crushing and screening process before being loaded on to a ship for export, in contrast to Magnetite, the other main type of iron ore that has to undergo a further round of processing before it can be used. This relatively simple extraction process also means that it is more time and cost efficient to mine than other types.
The large deposits of Hematite are extracted from altered banded iron formations and rarely igneous accumulations. It is typically found in places where there has been standing water or hot springs where it can precipitate out of the water and collect in layers at the bottom of lakes or other slow moving water features. Small crystals can also occur due to the weathering process of soils. It is possible for the mineral to occur without the appearance of water, too, usually as a result of volcanic activity. Interestingly, our planet is not the only one where Hematite has been discovered and two very large deposits have been found at the Terra Meridiani and Aram Chaos on Mars. The discovery was followed up by a Mars Exploration Rover and was found to be in the form of small sperules which analysis showed were concretions formed from a water solution which is clearly a significant discovery that suggest water was present on Mars at one time.
Obviously as an ore of iron, Hematite is mostly used in the production of iron and then used in the steel industry. There are other uses for the mineral, however, and Ochre is often made up of between 20% and 70% Hematite. Ochre has been used for many thousands of years as a dye and pigment. Indeed much of the old cave paintings use Ochre as colouration and mines have been found going back some 7,000 years. The mineral can also be used as jewelry and was probably at the height of its popularity in Victorian era Europe but there has recently been a bit of a resurgence in use as jewelry in the United States. It has even been thought to possess healing powers and some people use it in Feng Shui and it is also used as a paint pigment.