Geometallurgy relates to the practice of combining

geological Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth s ...

understanding with

metallurgical Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys. Metallurgy encompasses both the ...

test work and / or real time processing plant data (for extractive metallurgy), to create a geological based three-dimensional predictive model of

mineral processing Mineral processing is the process of separating commercially valuable minerals from their ores in the field of extractive metallurgy. Depending on the processes used in each instance, it is often referred to as ore dressing or ore milling. Be ...

response. It is used in the hard rock

mining Mining is the Resource extraction, extraction of valuable geological materials and minerals from the surface of the Earth. Mining is required to obtain most materials that cannot be grown through agriculture, agricultural processes, or feasib ...

industry for risk management and mitigation during mineral processing plant design. It is also used for production mine planning to optimize the ore feed to the processing plant. There are four important components or steps to developing a geometallurgical program,: *the geologically informed selection of a number of ore samples *laboratory-scale test work to determine the ore's response to mineral processing

unit operation In chemical engineering and related fields, a unit operation is a basic step in a process. Unit operations involve a physical change or chemical transformation such as separation, crystallization, evaporation, filtration, polymerization, isomeriza ...

s *the distribution of these parameters throughout the orebody using an accepted geostatistical technique *the application of a mining sequence plan and mineral processing models to generate a prediction of the process plant behavior

Sample selection

The sample mass and size distribution requirements are dictated by the kind of mathematical model that will be used to simulate the process plant, and the test work required to provide the appropriate model parameters. Flotation testing usually requires several kg of sample and grinding/hardness testing can required between 2 and 300 kg. The sample selection procedure is performed to optimize

granularity Granularity (also called graininess) is the degree to which a material or system is composed of distinguishable pieces, "granules" or "grains" (metaphorically). It can either refer to the extent to which a larger entity is subdivided, or the ...

, sample support, and cost. Samples are usually core samples composited over the height of the mining bench. For hardness parameters, the

variogram In spatial statistics the theoretical variogram, denoted 2\gamma(\mathbf_1,\mathbf_2), is a function describing the degree of spatial dependence of a spatial random field or stochastic process Z(\mathbf). The semivariogram \gamma(\mathbf_1,\ma ...

often increases rapidly near the origin and can reach the sill at distances significantly smaller than the typical drill hole collar spacing. For this reason the incremental model precision due to additional test work is often simply a consequence of the

central limit theorem In probability theory, the central limit theorem (CLT) states that, under appropriate conditions, the Probability distribution, distribution of a normalized version of the sample mean converges to a Normal distribution#Standard normal distributi ...

, and secondary correlations are sought to increase the precision without incurring additional sampling and testing costs. These secondary correlations can involve multi-variable regression analysis with other, non-metallurgical, ore parameters and/or domaining by rock type, lithology, alteration,

mineralogy Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical mineralogy, optical) properties of minerals and mineralized artifact (archaeology), artifacts. Specific s ...

, or structural domains.Preece, Richard. Use of point samples to estimate the spatial distribution of hardness in the Escondida porphyry copper deposit, Chile. International Autogenous and Semi-Autogenous Grinding Technology 2006, Vancouver, Canada, 2006

Test work

Geometallurgical test work is broken into those that impact

comminution Comminution is the reduction of solid materials from one average particle size to a smaller average particle size, by crushing, grinding, cutting, vibrating, or other processes. Comminution is related to pulverization and grinding. All use m ...

and those that impact recovery of the valuable component.

Comminution test work

The following tests are commonly used to generate inputs for geometallurgical modelling of comminution parameters, that is crushing, grinding and their associated energy use: * Bond ball mill work index test * Modified or comparative Bond ball mill index * Bond rod mill work index and Bond low energy impact crushing work index * SAGDesign test * SMC test * JK drop-weight test * Point load index test * SAG Power Index test (SPI(R)) * MFT test Dobby, G., Kosick, G., and Amelunxen, R. A focus on variability within the orebody for improved design of flotation plants. Proceedings of the Canadian Mineral Processors Meeting, Ottawa, Canada, 2002 * FKT, SKT, and SKT-WS tests * Geopyörä breakage test

Geostatistics

Block

kriging In statistics, originally in geostatistics, kriging or Kriging (), also known as Gaussian process regression, is a method of interpolation based on Gaussian process governed by prior covariances. Under suitable assumptions of the prior, kriging g ...

is the most common geostatistical method used for interpolating metallurgical index parameters and it is often applied on a domain basis. Classical geostatistics require that the estimation variable be additive, and there is currently some debate on the additive nature of the metallurgical index parameters measured by the above tests. The Bond ball mill work index test is thought to be additive because of its units of energy; nevertheless, experimental blending results show a non-additive behavior. The SPI(R) value is known not to be an additive parameter, however errors introduced by block kriging are not thought to be significant . These issues, among others, are being investigated as part of the Amira P843 research program on Geometallurgical mapping and mine modelling.

Mine plan and process models

The following process models are commonly applied to geometallurgy: * The Bond equation * The SPI calibration equation, CEET * FLEET* * SMC model * Aminpro-Grind, Aminpro-Flot models http://www.aminpro.com, 2009

Notes

General references

*Isaaks, Edward H., and Srivastava, R. Mohan. An Introduction to Applied Geostatistics. Oxford University Press, Oxford, NY, USA, 1989. *David, M., Handbook of Applied Advanced Geostatistical Ore Reserve Estimation. Elsevier, Amsterdam, 1988. *Mineral Processing Plant Design, Practice, and Control - Proceedings. Ed. Mular, A., Halbe, D., and Barratt, D. Society for Mining, Metallurgy, and Exploration, Inc. 2002. *Mineral Comminution Circuits - Their Operation and Optimisation. Ed. Napier-Munn, T.J., Morrell, S., Morrison, R.D., and Kojovic, T. JKMRC, The University of Queensland, 1996 Economic geology Metallurgy Mining Materials science