Artisanal mining is one of the basic mining activities that is carried out in Nigeria. It is a primitive way of extracting alluvial deposits from the earth. Nigeria has thrived well in certain sectors of the economy such as in the oil and gas sector, telecommunication, and recently, in the cement manufacturing subsector. Nigeria also produces over 2.6 million barrels of oil per day and has installed extensive oil and gas facilities which include nearly 200 flow stations, three (3) refineries, five (5) coastal terminals, extensive networks of pipelines, flow lines, and bulk lines (Ohimain, 2004), but in all this, the iron and steel industry remains dormant. Iron and steel are very important for both the growth and developing of any modern society because it plays a major role in the industrialization and infrastructural development of any nation. Nigeria has the potentials of becoming a great nation in West Africa sub-region but this can be made possible if the iron and steel industry is working again (Agbu, 2007), hence the need to revisit the mining sector.
The geology of the northern part of Nigeria
There are two distinct groups of granites in Northern Nigeria which differ considerably in age, structure, and mode of origin. These are the Older and Younger Granites which range in composition from granite to granodiorite with subordinate diorite and quartz – syenites. The Younger Granite is discordant, high level, magmatic intrusion with strong alkaline affinities. Jacobson (1963) have attributed the age of Older Granite to early Paleozoic whereas the Younger Granite is Jurassic. Falconer (1921) first recognized the essential difference between the Older and Younger Granites when minerals surveyed in the Northern Nigeria was established in 1911. According to Macleod and Turner (1971), they described the general geology of Jos Plateau and confirmed the presence of economic minerals such as cassiterite (tin) and columbite (niobium). Small amount of cassiterite-tin ore and columbite-tantalite are from the pegmatite associated with the Older Granite. Other environments that have the Basement Complex comprising of the pegmatite and migmatite are Nasarawa State, Kaduna State, etc.
The diverse rock types of Nigeria can be sub-divided into three main groups which are the Basement Complex, (ii) the Younger Granite, and (iii) the Sedimentary Series.
A good understanding of the rock type distribution is shown in Fig. 1 below.
Each group has its own associated meta-volcanic or volcanic rocks. Both igneous and metamorphic rocks of the Basement Complex and igneous rocks of the Younger Granite together occupy about 50% of Nigeria’s surface area while the sedimentary series occupy the remaining area (Ajibade et al., 1988).
Different states where cassiterite is mined in Nigeria
Artisanal mining of solid minerals like cassiterite started 1905–1972 rating Nigeria as the 6th producer of tin in the world while mining of columbite started from 1933–1945 rating Nigeria as the world exporter of columbite (Mallo, 2017. This activity still has its practice done in many parts of the states in the country and thus are the following: (1) Kaduna State: Artisanal mining of economic solid mineral like cassiterite and others are located in various local government of the state, places like Jaba, Jemaba, Kachia, and Ikara (NBRM 2012). (2) Nasarawa State: This state is also blessed with a lot of solid mineral deposits in places like Kama-Otto, Kwotto, and Angwan-Mada. These communities indulge in a lot of small-scale mining of cassiterite and Tantalite. (3) Plateau State: This state is called the home of tin because of its rich deposit of cassiterite both along the street of the state and also along stream sides due to alluvial deposition. Certain local government areas of the state that has the deposition of cassiterite are Jos-North, Jos-South, Barkin-Ladi, etc. States like Bauchi and others also have cassiterite deposits.
Associated minerals in cassiterite
Cassiterite is the chief ore of tin (Sn), but it houses other associated minerals such as columbite, wolframite, ilmenite, monazite, and others. When this mineral deposit (cassiterite) is mined from the earth by artisanal miners, it is further processed (either locally or industrially). The associated economic minerals that can boost the economy of this nation are thus discussed:
Tin (Sn)
Tin (Sn) is a chemical element belonging to the carbon family. It is a soft, silvery-white metal with a bluish tinge. Tin is widely used for plating steel cans used as food containers, in metals used for bearings, and in solder. Tin-plating of iron protects from corrosion.
Wolframite (Fe, Mn) Wo4
Wolframite is the chief source for tungsten (W), but other sources of tungsten are ferberite FeWO4 (60.5%) and hubnerite MnW04 (63.9). Wolframite and hubnerite constituent 75% source of world production of tungsten and scheelite has 25%. Impurities include magnesium (Mg), calcium oxide (CaO), tantalum oxide (Ta2O5), columbite oxide (NbOs), and tin oxide (SnO2).
Columbite (Fe, Mn (Nb2) O6 –Tantalite (Fe, Mn, Ta2O6)
Columbite is the most widespread niobium mineral and makes for an important ore of the industrially useful metal. Niobium, Nb, is used in alloys for improved strength. It also has shown superconductive properties. Tantalite replaces niobium in all properties up to 100%, and when tantalite exceeds niobium, the mineral is called tantalite, and when niobium exceeds tantalite, it is called columbite.
What is metallurgy?
Metallurgy is a domain of materials and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures which are called alloys. This also is the process that is used for the extraction of metals in their pure form from their ores.
Metallurgical operations
Various metallurgical operations that lead to obtaining pure metals from their ore are through the following steps: (i) crushing and grinding of the ore; (ii) concentration of the ore; (iii) roasting, calcination, and smelting; (iv) reduction; and (v) refining of the metals. After the mineral ore has been extracted, beneficiation is done either through the use of a magnetic separator or an air float machine. The following are the importance:
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(i)
Tantalite: They are used for the production of tantalum capacitor which is used in various electrical panels. They are very good in the electrical industries.
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(ii)
Wolframite: It is used for making ammunition and as an alloy.
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(iii)
Zircon sand: It is also used in the ceramics industry for the making of ceramics.
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(iv)
Columbite: It is used as a source of niobium as an alloy of steel to form weldable high-speed steel for radio transmitting valves, heat-sensitive detective devices called a barometer, for jet engines, and other aircraft components.
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(v)
Quartz: It is used in glass and silica bricks and paint scouring, soaps and paper. In its powdered form, it is used in porcelain paint, scouring soaps, and wood filter.
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(vi)
Tin: It is an alloy that is basically used to increase the strength of other materials. With this in view, if the Government of Nigeria take a proper record of the quantity of cassiterite mined from the various state, it would go a long way in reviving the various dead and lifeless milling industries.