Mineral exploitation

• Lasky's principle-

  • states that: in general as the purity of a mineral decreases the amount of the mineral present increases exponentially. So, the major problem with future mineral supplies is not the quantity that exists but the need to develop methods to exploit low-grade deposits
  • to help with estimates of future availability it is important to predict which deposits are likely to become exploitable in the future and when
• Reserves, resource and stock

  • the mineral deposits in the crust can be categorised according to whether the technology exists to exploit them and whether this exploitation would be economically viable
• Reserves vs resources

  
• Reserves, resource and stock-

  • mining companies have to plan many years head because it takes a long time to prepare a mine before any of the mineral can actually be extracted
  • this preparation includes gaining detailed information on the mineral that is to be mined
  • however the methods that provide this information are expensive especially trial drilling
  • deposits that will not be exploited in the near future may be investigated with cheaper methods that provide less detailed information
  • thorough exploratory investigations would be carried out nearer the time that exploitation take place
• Stock-

  • this includes all of the material that exists in the lithosphere and it includes the mineral that can be exploited now, that which will be exploitable when prices rise or new technologies are devloped and that which will never be technologically or economically exploitable
• Resource-

  • the resource is larger than the reserves as it includes all the material that is theoretically available for exploitation. This includes deposits that can be exploited now but with realistic increases in prices or improvements in technology could be extracted in the future
  • resources that are deep, low grade, in difficult chemical form or in locations that are currently protected could all become usable in the future
• Reserves-

  • the reserves are defined as the amount of the resource that can be exploited now using existing technology.
  • This means that while the size of the resource is finite the quantity counted in the reserves can change
  • for example, if the market price for the resource increases or if new ectraction technologies become economically viable then the reserves will increase and if market prices fall then reserves may decrease
• Categories of mineral reserves-

  • Inferred reserves: presence of the mineral can be predicted from knowledge of geological structures present but not enough is known to estimate the amount that can be economically extracted
  • Probable reserve: sufficient information about deposit is known the amount of the mineral that can be economically extracted can be estimated with sufficient accuracy that further exploration is justified
  • Proven reserves: sufficient exploration has been carried out, including trial drilling, accurately estimate the amount of the mineral that can be economically extracted
• Reserves limits-

  • the absence of the technology to exploit the deposits
  • the financial cost of exploitation may be too great
  • the environmental impact of exploitation may be unacceptable
• Mineral exploration-

  • Mineral deposits obviously cannot be extracted unless they have been found. Discovering deposits involves a variety of exploratory techniques
  • remote sensing involves any technique that give information without taking direct samples. the sensing can be done at different distances from the deposits, collecting data on a range of scales: satellite surveys, aircraft surveys or ground-based surveys
  • larger scale surveys may be more expensive but they are often very cost effective, providing a lot of information at a relatively low cost per unit area that is surveyed
• Survey techniques-

  • IR spectroscopy= different minerals emit infrared radiation at different wavelengths, these can be used to identify them
  • Gravimetry= Gravimeters detect variations gravity caused by variations in density and mass. Igneous rocks usually more dense than sedimentary deposits
  • Magnetometry= Magnetometers detect rocks are more magnetic such as the iron ore magnetite and ores of tungsten cobalt
  • Seismic surveys=involve sound waves produced by controlled explosions, or a seismic vibrator on the surface. the echoes can give information about the depth, density, shape of rock strata
• Survey techniques-

  • Resistivity= is the measurement of the difficulty with which electricity passes through a material. in general sedimentary rocks have lower resistivities than igneous rocks because they have higher water contents
  • Trial Drilling= the most expensive technique per sampling site but its is the only method that actually produces samples of the rocks underground
  • Chemical Analysis= Laboratory tests confirm the chemical compositions and purity of the minerals in the rock samples
• Factors affecting mining viability-

  • proving the presence of a mineral does not mean that economic mining activities can start, a number of factors must be considered to assess the viability of a mine
• Ore purity-

  • the purity of the ore affects the financial costs of exploitation and the environmental impacts of mining
  • if the ore grade is low then:
  • more rock will have to be mined
  • more waste materials (spoil) will be produced
  • more energy will be needed for mining and processing
  • more pollution will be generated
• Chemical form-

  • the chemical form of the mineral ore affects the ease of chemical extraction of the metal
  • for example, aluminium can be extracted from bauxite(aluminium oxide) but not from clay (alumino-silicates) which is much more abundant
• Overburden and hydrology-

  • the overburden is the rock that lies above a mineral deposit
  • hard overburden may require blasting which increases cost
  • loose overburden may increase the risk of landslides so the sides of the mine void may have to be landscaped at a more gentle gradient
  • this may increase the overall area of the mine
  • higher precipitation or impermeable rocks below may increase drainage costs
• Depth-

  • costs rise rapidly as the depth increases. if the depth is doubled then the cost much more than doubles
  • the sides of the mine cannot be vertical because the risk of collapse
  • so the amount of rock that must be removed to reach the mineral rises rapidly as depth increases
  • as depth increases the amount of water that flows into the mine from surface runoff or groundwater also rises increasing the pumping costs significantly
• Cut off ore grade-

  • mining has to be an economically profitable activity so there must be a balance between production costs and income
  • the lowest ore purity that can be mined economically using existing technology is called the COOG and it changes as technology improves and market prices fluctuate
• COOG changes-

  • Higher market value=COOG decreases
  • Lower market value=COOG increases
  • Improved extraction technology=COOG decreases
  • Higher energy costs= COOG increases
• Transport costs-

  • transport costs are effected by the distance to the market, the ease of bulk transport, the presence of a suitable transport infrastructure and whether the bulk of the mineral has been reduced by processing
• Market economics -

  • the market demand and sale value of the minerals control the economic viability of exploiting a specific mineral deposit
  • the market price is controlled by the demand for the mineral, how much is produced and the costs of extraction and processing
  • the amount that can be supplied increases relatively slowly as mines are developed but demand can rise and fall quickly
  • so which demand and supply do not match prices can fluctuate widely
• Market economies continued-

  • this uncertainty makes the prediction of future markets very important
  • exploiting deposits in regions with exisiting mining activities produces benefits by having access to the exisitng infrastructure for transport and energy, equipment supplies, and a trained workforce