Mining industries are viewed as major key drivers of economic growth and in the development process of a nation. Bradshaw (2005), it can also be seen as the lead sector that drive economic expansion which can lead to higher levels of social and economic well being. Bridge (2008)
Many countries of the world like Australia, Canada, Russia, India, Saudi Arabia and Botswana have depended on solid minerals wealth to finance their societies.
The rising demand for primary commodities from fast-growing and emerging countries, like China, has added to the persistent high level of solid mineral in developed countries. UNCTAD (2007). Likewise, high prices and demand of solid mineral have stimulated an investment surge in mineral exploration and production in particularly the developing countries. Okeke (2008)
The Younger Granite rocks of the Jos Plateau and surrounding areas are richly mineralized with cassiterite. Cassiterite is associated with other minerals such as columbite, monazite and accessories like zircon and topaz. As a result, a lot of mining activities such as formal and informal mining have been carried out over the years in the area. Presently, most of the mining activities carried out are still by trial and error means such has lotto mining.
Cassiterite within the study area are obtained from shallow alluvial deposits notably from the river system of the Delimi, Jaura and Asob whose sources are from Jos Plateau. The Tin was smelted at Liruei Delma in Bauchi and the smelted Tin was used for the production of Tin straws. The products which could have been used for the production of arrows and other implements were marketed at Kano, the Southern markets of Ilorin and Lagos as far back as the late 18th Century.
More than 90% of the cassiterite produced in Nigeria was mined from Jos Plateau area. The mining area extends to the South as far as Wamba, the West to Kafanchan, in the North to Bura and in the East up to the Jarawa Hills. The maximum extent of the Tin producing area on the Jos region amount in longitudinal direction to about 240km and latitudinal direction to about 120km. Large scale mining of the mineral started about 1911 and Nigeria was ranked as the world sixth Tin producer and the largest producer of Columbite. Tin production on Jos Plateau increased rapidly from 1.36 tons in 1904 to 5,573 tons ten years later reaching its peak production level of 15,842 tons in 1943. Mallo S.J (2007).
The Geologic map showing the various rock distributions and various mineral deposit in the study area is seen in Fig. 1.
2.1 DEFINITION OF MINERAL PROCESSING
Mineral processing also known as mineral dressing or ore dressing is the process of separating commercially valuable minerals from their ores. (Miettinen et.al., 2010).
Before the advent of heavy machinery, the raw ore was broken up using hammers yielded by hand, a process called “spalling”. Before long, mechanical means were found to achieve this process. Mineral processing thus includes the following:
Comminution- This is the action of liberating valuable mineral from it associated gangue through crushing and grinding.
Separation – This is the action of separating valuable minerals through the application of individual force that differ in magnitude and direction.
2.2 THE MINERALS
The following minerals obtained from cassiterite are: Tin (Sn), Columbite (Fe,Mn (Nb2)O6, Tantalite (Fe,Mn, Ta2O6), Wolframite (Fe, Mg) WO4 etc.
Comminution involves a process in which solid materials are reduced in sizes by Crushing and Grinding. It occurs naturally during faulting in the upper part of the earth crust and it is an important operation in mineral processing, ceramics, electronics and other fields. Within industrial usage, the purpose of comminution is to reduce the size and to increase the surface area of solid. It is also used to free useful materials from matrix materials in which they are embedded. During this process, mineral processing plant is subjected to two processes of comminution which are Crushing and Grinding. Balasubramanian (2017)
Crushing is the first mechanical stage in comminution process and the sole objective of such operation is the liberation of valuable minerals from the gauge. It is carried out in heavy, slow moving equipment in which the breaker faces are mechanically prevented from making contact with one another. Crushing is classified into Primary and Secondary Crushing. Balasubramanian (2017)
This is the last unit operation in the comminution process. It is concerned with the final stage of size reduction into powdered form and it is done by a combination of impact and abrasions (dryer on water suspension). The optimum size of release is determined by both technical and economic considerations. The finer the ore, the higher the cost. Finer grinding usually results in improved value recovery. Grinding is performed on tumbling mills and also, it can be done using a pulverizer. Balasubramanian (2017)