Sampling is used to estimate grades and contents of materials in a deposit. The objective is to do this in an unbiased, precise manner. There are different sampling methods depending on the type of deposit, including core drilling, channel sampling, and trench sampling. Samples are analyzed to determine their physical and chemical characteristics, which provides information about the deposit for resource evaluation and process design.

2. • Generally sampling is the art(process) of selecting a
part of a whole such that the measured value for the
part is an unbiased estimate for the whole.
• The objective of sampling in mineral processing is to
estimate grades and contents of sampling units in an
unbiased manner and with an acceptable and
affordable degree of precision.
• In mineral processing a whole is referred to as a
sampling unit.
• A sampling unit is classified as a dynamic stochastic
system when sampled during transfer, and as static
stochastic system when sampled whilst stationary.

3. • Mineral deposits are sampled for several
reasons including:
Resource evaluation
 Determination of the physical and chemical
characteristics of material,
 And process amenability.

4. • In Placer deposits.
• In simple bedded deposit.
• In copper & other sulphide ore deposit.
• Deposits that are not homogeneous.

5. • Core Drilling
• Reverse circulation drilling
• Auger Drilling
• Other drilling methods
• Channel Sampling
• Trench sampling
• Geochemical and environmental Sampling
• Water samples
• Run of mine ore feed
• Crusher product sampling

6. • This is the preferred method of recovering material
from within the ore body and is also the most
expensive.
• Generally between 27 mm to 100 mm in diameter.
• Cores are generated using a circular drill bit that
allows a cylinder of rock to rise
• Within the interior of the drill steel as the drill
progresses.
• The resulting drill core generally has a smooth
surface and is consistent in diameter along its length

9. • Operates in the same manner as holes drilled for
general purpose viz. boreholes
• Less expensive than core drilling
• The samples from each drill interval are logged
separately as they come from the hole.
• RC is not recommended when the exact transition
from one rock to another is required viz. coal.

10. • When material is unconsolidated Auger drilling
method is used.
• Soils, placer deposits of river gravel, and previously
placed material such as mine waste dumps and
impoundments.
• The sample may consist of the entire amount of
material extracted from the hole or a hollow tube in
the middle of the drill stem can be used to collect
materials from only desired depths.

12. • Chip and mud samples are collected from ordinary
rotary drilling
• Which are less expensive but also less reliable and
are used for indicative purposes only.
• Specialized drills for collection of large pieces of
rock such as placer sampling are also used.

13. • Where the material to be sampled is exposed to
the surface or in underground workings, channel
sampling is used.
• In this procedure a channel of dimensions similar
to the diameter of the core or RC hole is excavated.
• The resulting samples are chips similar to those
recovered through RC drilling.
• Channel samples have the advantage over RC
samples in that the material can be geologically
logged prior to excavation.

14. • Where the material to be sampled is close to the
surface, trenches are excavated to gain access to the
material and samples are taken either as channel
samples within the trenches or as selected samples
of the excavated material.
• This results in broken material

15. • Grab samples on a random basis as it is mined or
transported.
• Such samples maybe useful for obtaining overall
averages for large amounts of material but not
Useful for identifying material characteristics at a
specific location.

17. • Expandable cylinders to measure rock strengths
and stresses.
• Gauges to measure ground water levels
• Sophisticated tomographic techniques use sensors
placed in multiple drill holes to provide detailed
information on the material between the drill holes.
• Work is underway to develop sensors that will be
able to detect the presence of metals.

18. • Drilling samples both core and chips are logged in
order to record the material characteristics along the
drill hole.
• Samples are logged for:
 Rock types
 Alteration types
 Association of various minerals
 Estimated content of the desired commodity
Core samples are also logged for:
• fracture spacing and intensity,
• Rock quality designation
• And fracture orientation
• Photographs are also taken of the core.

19. The analysis includes:
• moisture content
• Total metal content
• Soluble metal content
• Content of non-metal
commodities
• Heat content for coal and
oil shale
• Ash content after
combustion
• In situ density
• Porosity
• Permeability
• Compressive strength
• Compaction
• Grinding index

20. • Direct measurement of mineral types is possible
using QEMSCAN.
These images can also be processed to provide
information on:
• modal abundance
• Grain size
• Mode of occurrence
• Liberation characteristics
• And quantity of mineral phase recoverable.

21. Sources