1.0 Introduction
1.1 Overview
Iron constitutes about 5% of the Earth's crust, making it the fourth most abundant element. Iron oxides and hydroxides form the principal iron ore minerals, due to their high iron content and occurrence as large tonnage surface deposits. The presence of the amount of iron varies from an average of 2-3% in sedimentary rocks to 8.5% in the basalt and gabbro. Iron is, however, present in low concentration in most parts of the earth, thus a deposit must have a high percentage of the metal to be considered ore grade for economic purposes. Typically, a deposit must contain at least 25% iron to be considered economically recoverable. Exploitation of large, low grade iron ore deposits can be achieved through concentration of the iron.
The iron itself is usually found in the minerals of magnetite (Fe3O4), hematite (Fe2O3), goethite (FeO(OH)) or limonite (FeO(OH)n(H2O)), siderite (FeCO3), chamosite (Mg,Fe,Al)6(Si,Al)414(OH)8, ilmenite (FeTiO3) and pyrite (FeS). Despite the existence of iron in many minerals, five of them are the primary sources of iron: magnetite (Fe3O4), hematite (Fe2O3), goethite/limonite (FeO(OH)), siderite (FeCO3), and pyrite (FeS).
Iron ores are rocks and minerals from which metallic iron can be extracted. An iron ore deposit is a mineral body of sufficient size, iron content, and chemical composition with physical and economic characteristic that will allow it to be a source of iron either immediately or potentially. Iron ore is the raw material used to make pig iron, which is one of the main raw materials to make steel. Nearly 98% of the mined iron ore is used to make steel. There are four main types of iron ore deposits worked currently, depending on the mineralogy and geology of the ore deposits. These are magnetite, titanomagnetite, massive hematite, and pisolitic ironstone deposits.
The Itakpe iron ore deposit in Nigeria which has a total estimated reserve of about 182.5 million metric tonnes consists mainly of quartzite with magnetite and hematite.
The deposit has been developed to supply iron ore concentrates to Ajaokuta steel plant and the Delta steel plant, Aladja, in Nigeria.
The Itakpe Iron deposit is important for the successful development of iron and steel industry in Nigeria though on the national scale there are other silico-ferruginous formations which are interesting from commercial and economic viewpoint especially the deposits of Ajabonoko Hill and Choko-Choko which are said to be similar to those at Itakpe. To be taken seriously also is the revenue loss due to the uncovered minerals in Itakpe iron ore gangue.
The extraction of specific value minerals from their naturally occurring ores is variously termed “ore dressing,” “mineral dressing,” and “mineral beneficiation.” For most metalliferous ores produced by mining operations, this extraction process is an important intermediate step in the transformation of natural ore to pure metal. Although a few mined ores contain sufficient metal concentrations to require no beneficiation (e.g. some iron ores), most contain relatively small amount of the valuable metal, from perhaps a few percent in the case of base metals which are commonly intergrown with economically important and unimportant (gangue) minerals on a microscopic scale in the iron ore gangue.
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