JOMO KENYATTA UNIVERSITY OF AGRICULTURE AND TECHNOLOGY
DEPARTMENT: MECHANICAL ENGINEERING
COURSE: MINING AND MINERAL PROCESSING ENGINEERING
NAME: OMBIRO SAMMY O.
UNIT: SELECTED MINERAL MINING METHOD I
THE KENYA FLOURSPAR
The fluorite (CaF2) deposits were discovered by prof. Al Amin in 1967 in the areas of Kimwarer, Choff and Kamnaon. He was searching for semi-precious stones, and initially mistook the purple fluorite for gemstone. He therefore collected the sample and took them for analysis in Mombasa. It was later found to be fluorite. A hand-mining operation was started and the fluorspar was supplied to the Bamburi Portland Cement Company in Mombasa. At its peak, the operation, which relied on donkeys to transport the fluorspar, produced around 400 tons per month of high grade fluorspar. In 1971 the Fluorspar Company of Kenya (FCK) was established, under the auspices of the Kenya government, to exploit the deposits on a larger scale. Crushing and jigging plants were later put up at mining site for large scale production of the metallurgical grade. Kenya fluorspar was a state parastatal upto 1996 when it was privatized. It is currently owned by local and foreign investors. The company has seven active mining sites available from which ore can be mined depending on the grade and quality required. In 2003 the company obtained made a major investment in earth-moving equipment and plant upgrading. The deposit has been commercially mined since 1971. Initially, metallurgical grade fluorspar was produced. In 1975 a 100,000 ton per annum acid grade fluorspar concentrator was commissioned and by 1979 metallurgical grade fluorspar was no longer produced as primary product, but can still be produced as secondary product for smaller consignments.
The Kimwarer ore deposit has now been mined for over 35 years It is an EPZ (Export processing zone).
Kenya Fluorspar is a concern based in the Kerio Valley in the district of Eldoret and Iten. FORMATION OF FLOURITE (CaF2)
The fluorite is an industrial mineral formed 150 to 200 million years ago. It is formed by replacement reaction known as mesomatism. The magma or hot water containing fluorine and other minerals was forced up from deep within the Earth. When this brine reached the calcium rich, limestone bedrock (CaCO3), fluorite crystals formed along the walls of fractures and voids in the rock. Flat layers of fluorite also formed parallel to the limestone beds, replacing the host rock. The fluorine replaced the CO32- from the CaCO3 to form CaF2. The CO32- was dissipated as CO2 and water. This process is further elaborated in equation below: Ca2- + F22- CaF2 (fluorite)
GEOLOGY AND OCURRENCE
Fluorite (also called fluorspar) is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon. Crystal twinning is common and adds complexity to the observed crystal. The fluorite deposits are believed to be of hydrothermal origin in the Post-Miocene era when lavas formed a protective cap over Precambrian rocks in the area.
The main deposit of fluorite is located at Kimwarer and is exposed on a series of five hills, four of which have been mined. Two other minor deposits knows as Choff and Kamnaon are approximately 2 to 5 km north of the present mine site and have been partially mined in the past for the production of metallurgical-grade spar.
The Kimwarer ore bodies contain by far the largest ore reserves. The ore body contacts are distinct due to the buff colour of the ore in contrast to the grey gneiss, white marbles or pegmatites. Typically the fluorite is finely crystalline and disseminated through a siliceous matrix. Zones of high grade ore are often purplish or creamy yellow in colour with cavities filled with distinct cubic crystals.
The Choffs have two ore bodies running parallel to...
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