Iron ores of diverse quality and origin are found in Nigeria. The purest ores occur in a series of e basement ridges known as the Itakpe Hills in Kogi if State. The iron and steel industry, near Ajackuta, exploits this deposit. In the Itakpe iron ore, magnetite and hematite are the main ore minerals. Proven Iron Ore reserves are at least 200 million tonnes with a life-span of over 100 years. The cornmercial ore grades range in ferrous (Fe) content e from rich ores with over 50 per cent Fe, mediurn grade ores (30 - 50 per cent Fe), to poor ores (25 n - 30 per cent Fe).
Mining is undertaken by the e National Iron Ore Mining Company for the Ajaokuta Steel Plant and for the production of super-concentrates at 68 per cent Fe, for the Delta Steel Plant at Aladja near Warri. Although Nigeria's interest in the iron and steel industry dates back to the close of the colonial era, it was not until 1982 that a direct reduction steel a plant was commissioned at Aladja, using imported iron ore from Liberia and Brazil, and limestone from Mfamosing near Calabar.
Primary steel billets are e produced at Aladja for steel rolling mills at Katsina, ». Jos, Oshogbo and Eket. Large reserves of sedimentary iron ore are exposed at Agbaja Plateau in Kogi State, where oolitic and pisolitic iron-stones, rich in phosphorous and alumina, hold up to 30.5 million tonnes which assay 50 per cent Fe. Other major sedimentary iron deposits are found in the Nupe basin, Sokoto basin and at Enugu. Other ferrous metals useful in the iron and steel industry are also found in Nigeria.
Columbite, the ore for niobium, occurs in association with tin deposits on the Jos Plateau, and in Bauchi and Kano States. Nigeria is among the world's leading exporters of columbite with proven reserves of 14,000 tonnes. Manganese, molybdenum, tungsten and titanium are other metals of the ferro-alloy group that are known to exist in the country. Wolframite, the ore of tungsten, occurs in primary veins with tin in the younger granites, from where molybdenum has also been mined on a small scale.
Among the non-ferrous metals only tin, lead and zinc are mined in Nigeria. Tin has been mined since colonial times and is one of the most versatile metals commonly used in industry. Tin ore (cassiterite or tinstone) is obtained mostly from the younger granites in the northern parts of the country and has been largely won from old stream channel deposits (placers) on the Jos Plateau and around younger granite masses in Bauchi, Kaduna, Kano and Benue States. Pegmatites in Cross River, Oyo, Niger, Kwara and Plateau States had also supplied tin in the past.
Prior to 1975, Nigeria was a major tin exporter with an annual production of tin concentrates which peaked at about 11,000 tonnes. This has now declined drastically to about 2,000 tonnes. Among the factors accounting for the collapse of the tin industry in Nigeria are the depletion of the readily accessible placer deposits and the prohibitive cost of mining the ores beneath the basalt flows on the Jos Plateau. There has been, in recent times, renewed interest in tin mining in Nigeria and the Nigerian Tin Mining Company has put the proven tin reserves on the Jos Plateau at about 31,773 tonnes.
Lead and zinc ores are usually found together. They occur in commercial quantities in the Benue Trough, in a narrow belt over 560 km stretching from Ishiagu in the south-east to Bauchi State. Small-scale mining has been carried out in Abakaliki area, where reserves of about 100,000 tonnes of lead and 80,000 tonnes of zinc have been estimated. Other major lead-zinc occurrences are atAmeka, Ameri in Ebonyi State, Arufu and Zurak in Taraba State. However, lead-zinc mining in Nigeria has been rather intermittent.
Gold and silver have been mined in Nigeria for a long time. Abandoned colonial gold camps exist around Sokoto, Kaduna, llesha and Calabar. About 12 tonnes of gold were produced in 1913. The Nigerian Mining Corporation has recently reinvestigated the llesha gold mines. Small amounts of silver are associated with the Nigerian gold and also with lead-zinc ores. while silver occurs in the Zurak lead-zinc deposit.