Mining

Introduction to mines:

              Mining is the extraction of minerals and metals from earth.  Manganese, tantalum, cassiterite, copper, tin, nickel, bauxite (aluminum ore), lead, iron ore, gold, silver, and diamonds are just some examples of what is mined. 

              In order to develop mines we have to understand the geology of the area. The formation of ore body is important in this respect. An ore is considered to be an aggregation of minerals from which a metal or metallic compound can be recovered economically on a commercial

scale. 

              When the percentage of metal or valuable in the ore is too low for profitable recovery, the rock ceases to be an ore. A mineral may be regarded as a naturally occurring chemical compound having a definite

chemical composition and crystal structure. The physical properties of minerals play the most important role in the economic processing of various ores.

Physical properties of minerals :

              The physical properties of minerals can be determined without the use of chemical tests.They depend upon the kinds and arrangement of atoms in their crystal structures. The various physical properties of minerals include transparency, luster, colour, specific gravity, hardness, cleavage, fracture, magnetic properties, electrical properties, radioactive and optical properties.

Transparency

                 This term used to describe the case with which we can see through a mineral. Three terms for transparency are in common use i.e. opaque, transparent & translucent. The opaque minerals are those through which no light can be seen. Transparent minerals are those which can be seen through clearly. Translucent minerals are those through which a little light can be seen.

Luster

                  This may be defined as the amount and quality of the reflection of light from mineral surface. The luster of mineral refers to its surface appearance.

Colour

                  In most cases the colour of mineral is due to absorption of certain wavelength of light energy by the atoms making up the crystal. The remaining wavelengths of the light that are not absorbed give the sensation of colour to the eye.

Luminescence

                 This refers to the emission of light by a mineral which is not the direct result of incandescence. Luminescence in most minerals is faint and can be seen only in the dark. Minerals which luminance during exposure to ultraviolet light and x-rays, are called fluorescent.

Specific Gravity

                  Specific gravity of a particular mineral is practically constant, it may vary a little with the presence of some impurities. The difference in specific gravity affords one of the surest means of separating minerals from each other and has been put to practical use. Simple washing in water affects an efficient separation of gold grains from quartz sand, whereas use of heavy liquids affects the separation of lighter coal from heavier shale. Difference in specific gravities forms the basis of a class of ore-dressing process known as ‘gravity

concentration method’.

Hardness

                   This may be defined as the ability of a mineral to resist scratching. This is different from the ease with which it can be broken. Diamond is one of the hardest material known, but it can be shattered easily. Like other physical properties, the hardness is dependent on the kinds and arrangements of atoms in mineral structures. The basis of the test is a set of minerals selected by the Austrian mineralogist, F. Mohs in 1974 numbered 1to 10 in order of increasing order of hardness.

Mohs scale of Hardness

1. Talc 
2. Gypsum
3. Calcite 
4 .Flourite
5. Apatite 
6 .Oligoclage
7 .Quartz 
8 .Topaz
9. Quarandum 
10 .Diamond.

Logging

                 The purpose of logging is to determine the thickness of ore body/coal seam and also to ascertain the quality of the ore/coal. For this purpose a bore hole is driven down the hole through core drilling and core is recovered which is placed in a core box with utmost care. The geologist/mining engineer measure the core length of the earth crust carefully and a picture is drawn on paper of the length and location of the ore body/coal seam.

           Simultaneously ore/coal seam sent to laboratory for quality analysis. This provides the basic information for the Geological and Assay database for any mining software like surpac , datamine to be used for the Reserve estimation, establishing average quality , Ore modeling ,preparation of the mine plan and finally the mine scheduling to produce targeted quantity of Ore with stipulated quality. Bench wise excavation plan To meet the targeted production with desired quality a systematic and scientific bench wise excavation plan is prepared synchronizing the overburden removal to expose sufficient ore benches for the desired production and excavation from different ore benches of different ore quality which can be blended at the crusher level for the desired final product for dispatches to the steel plant.

Reading of excavation plan

              The size and shape of topography where mining is to be carried out is depicted in a mine surface plan which is drawn on a suitable scale together with every surface features in a schedule manner called mine surface plan. The various surface features are shown according to a specified schedule under the statute. Excavation plan can be prepared on the mine surface plan or separately on mine working plan showing all the mine working benches/faces clearly demarcating the area with the length and breadth of the planned excavation in particular stipulated period. Normally excavation plan is prepared every month with respect to the annual excavation plan under five year Mining Scheme approved by Indian Bureau of Mines. Excavation plan can vary with deviations in the requirements,but annual planned quantity shall not be increased more than the quantity stipulated in the mining scheme without the permissions of IBM.

Short & Long term excavation plan

Long term plans

                  All the long term excavation plans has to be made in line with the mine plans, mining scheme and the mine closure/progressive mine closure plans approved by IBM.Progressive Mine Closure Plan is the essence of mine planning in which the planning starts from the final pit limit at the end of mine life with systematic reclamation and rehabilitation so that at the end it is restored to the original land form as far as possible.Mine Plan is the plan of systematic excavation plan for the applied lease period normally for 20 years with due considerations of the Environmental protection and the mineral Conservation. There are always possibilities of the deviations from the mine plan if there are shortages from the target or any changes in demands.

Mining Schemes

                  To accommodate the deviations from the original mine plan a Mining Scheme is prepared after every 5 years of the Mine Plan period.. Five year mining scheme shows the modified mine excavation plan with clear details of each year excavation. All the plans are prepared for mining of ore body/coal keeping in view the objective and mission of our Company. In long term plan Govt. of India five years plan in the development of society & our Country are also taken care of. For example vision 2025 have been drawn where steel production is augmented to 100 million tones in India. Short term plans In order to reach the goal and to fulfill the objective of the Organization based on the long term excavation plan like the mine plan and the mining schemes, short term plan is prepared for annual/monthly excavations where every detail is worked out.

MINES OPERATION

                Ahead of the mine production faces in different benches, a drilling block should be maintained of sufficient length and width in all the faces to manage quantity of material at least for one week. This enables easy weekly blasting and prevents from frequent shifting of the machines. For good blasting efficiency effective drilling parameters should be followed. Drilling parameters are dependent on the rock characteristics. Distance from the free face to the first line of the holes is known as Burden, hole to hole distance in a row is called spacing and the extra drilling more than the height of the bench is called the subgrade drilling. Drilling block is properly leveled with the use of a dozer and prior to start of the drilling operations, positions of the drill holes are physically marked on the ground as per the desired drilling parameters. Drilling parameters can be fixed on the trial and error basis following the general prescribed thumb rules. Harder rock requires smaller burden and spacing while the larger spacing and burden can be given in the soft rocks where less

energy is required for breaking of the rocks.

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