# ORE RESERVE ESTIMATION TECHNIQUES

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__ORE RESERVE ESTIMATION TECHNIQUES__

__ORE RESERVE ESTIMATION TECHNIQUES__

The main objective of ore reserve estimation is to acquire as much information as possible form sampling and estimate the tonnage and grade (value and extent) or the ore deposit. In order to achieve this, geologist organize detailed sampling procedures to follow.

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**Sampling**

Conclusive evidence of the existence of an ore body requires that samples, representative of the whole, be collected and analysed. Mineral samples are obtained by excavation or drilling. If the deposit is exposed or located at shallow depths of burial, an opening is excavated from the surface in the form of a channel, pit or trench. Drilling small circular holes from the surface into the deposit is by far the most expeditious and economical mean of sampling an ore body that extend to depth. Over 95% of mineral sampling today is done by drilling.The three most common drilling methods employed purpose today are:

- Diamond drilling
- Auger or Roller Bit rotary and
- Percussion drilling

- Regular (rectangular/square, triangular and polygonal)
- Irregular

Initially geologic conditions may favor an irregular grid but a regular grid is to be adopted as early as feasible. The reason is that it provides uniform level of knowledge of all parts of deposits and enhances visual interpretation of results.

__Reserve Estimation__Upon completion of sampling and sampling results become available, the next step is estimate as accurately as possible the ore reserve. Ore Reserve estimation is a procedure that starts at exploration and continues throughout the life of a mine with constant improvement and refinement in the methods employed. Thus increasing the confidence and establishing a competent geologic database of the ore deposit. Data from the ore reserve estimation are the basic input for feasibility study of a proposed mining project.

There are two broad techniques employed in ore reserve estimation;

**Classical****Geo-statistical**

**Classical Technique**

**Polygon method***areas of influence polygons are assigned to drillholes either on plan or cross section and reserve calculations are done thereon.*

**Triangle method***a modification of the polygon method, differs from it by constructing triangles with the drill holes forming the apices of the triangle. The advantage is the the data in three point holes enter into the calculations and then proceed the same manner as in polygon method*

**Section method***blocks of ore are outlined on regularly or evenly spaced cross sections of the ore body. Areas of influence are calculated from the same way and all calculations are tabulated.*

**2. Geo-statistical**

This technique involves the application of mathematics of random functions to the reconnaissance of mineral deposits. Usually this procedure entails these steps;

- Study of geologic controls on mineralization and any zones of the deposit
- Computation of variograms (graphical correlation of mineral characteristic) for each geologic zone
- Division of ore body into matrices of blocks for kriging (calculation of block grade related to adjacent samples); blocks are then classed as measured, indicated and inferred
- Estimate of tonnage and grade of each block at given cut-off-grade
- Printing of recoverable grade distribution plans by level or bench in the proposed mine.

ORE RESERVE ESTIMATION TECHNIQUES
Reviewed by CEDRICK KAU
on
March 01, 2016
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