Sampling techniques for mineral deposit

CONTENTS
 Introduction
 Sample Definition
 Basis of Sampling
 Sampling Equipments
 Types of Sampling
 Methods of Sampling
 Errors in Sampling
 Conclusion
 References

Introduction
 Sampling of minerals deposits is an important aspect
of geological exploration. Which involves the process
of collecting lots or portions of productive rocks or
ores. The main purpose is to determine the quality (or)
composition of a material. According to ‘Boxter and
park’ sampling is defined as “ the process of taking a
small portion of an article such that a consistency of
the portion shall be the representative of whole”.

Sample Definition
 Sample ,which is a finite part of a statistical
population whose properties are studied to gain
information about the whole. .The value of a
sample depends on the volume or quantity of
material which actually represents and the
degree of accuracy it represents.

Sampling Equipments
 As we know for successful sampling procedure the
following pieces of equipment are necessary. The
equipments are depends on which method we apply for
sampling. Some of the equipments are scoop,
Canvas sheets, sampling buckets, clear sample bags,
pocket compass, measuring tape, aneroid barometer,
large boxes with locks, twine, wax, seals, pencil, liner
sleeping tags ,drill rods,spear,brushes etc……..
 In addition, if the mine is in operation the following
equipments are used like hammers and picks, drills,
gads, brushes, moils, shovels, brooms, transits miner
pick mechanical dividing sampler etc……

Basis of Sampling
For the analytical results obtained to have any validity or meaning
it is essential that appropriate sampling procedures be adopted.
Thus sampling methods have 3 main groups.
 Those in which all the material is examined.
 Causal sampling on ad-hoc basis.
 Methods in which portions of the material are selected based on
upon statistical properties.
The method 1 is impracticable due to its excessive material and
time consuming for analysis, method 2 is a unscientific in this
case as the taking of sampling is entirely casual, any true form of
analytical control or supervision is impossible, a method 3 is only
reliable basis for sampling based on statistical probabilities. Here
small portion is analyzed first and then go for further sampling
plan .

Types of Sampling
 In sampling we have mainly three types they are :
 Chemical sampling:- In chemical sampling the samples
are taken for assaying and determining the content
valuable and deleterious components in the body of the
useful minerals.
 Technological sampling:- In this method samples are
collected for the study of technological properties of the
raw material made in the course of its beneficiation and
processing .
 Technical sampling:- Samples are taken to study a
technical properties of raw materials which does not
requires metallurgical or chemical treatment.
(Mineralogical sampling, Geo-physical sampling)

Methods of Sampling
 Sampling methods vary from simple grab samples on
existing exposures to sophisticated drilling methods.
Generally there are two sampling methods such as :
 Surface sampling
 Under ground sampling
In any method of sampling , the records kept are as
important as in the field practice it is used. Here ,type of
sample, size of sample, true thickness of vein, intervals
between sample location, naming of samples date and
other relevant data are to be recorded. Experience in
sampling profession provides for deciding the proper
spacing and number of samples to be taken and selection
of methods .

 Continue…….
 The important surfacial
sampling methods are
as follows:
 Channel sampling,
Groove sampling, chip
sampling, Muck
sampling, grab sampling,
Car sampling and chute
sampling
 Drill whole sampling

continue……
The some of important underground
sampling methods.
 Face sampling
 Regular channel or groove sampling
 Pick sampling
 Grab sampling
 Muck- pile samples
 Car and chute samples
 Bulk sampling
 Drill sampling
 Churan drill samples
 Diamond drill samples
 Rock drill samples (with piston/hammer drill)

Grab sampling
 As the term indicates that grab sampling is not true
sampling. A specimen picked up from ore or a mineral
deposits or a portion of mineralized rock, which taken
out of an ore body are called grab samples. The samples
are taken and analyzed to obtain a preliminary idea
about the nature and grade of whole deposit a, to know
appreciate metal content.

Channel or Groove or Trench
Sampling
 It is the most accepted method of sampling which
best suited to bedded, banded and vein type of
deposits, this method consist of cutting channels
across the face of exposed ore and collecting
resulting chips, fragments and dust from each
channels to make a sample. In some cases the
channel may also be cut along a line making a
small angle with thickness of deposit The process
involves the following steps.

Continue……
 The exposure is cleaned first and remove the
unwanted materials.
 If necessary the rock face may be trimmed at cutting
point of the deposit.
 The location of channel is marked by a set of parallel
lines.
 The inner part is excavated keeping a constant channel
cross section.
 Finally excavated material is collected, pulvariesed
carefully and sampling site is labeled. The cutting of
channels depends on ore body or metal deposit.

Chip or point sampling
 The method is less laborious and used as a regular
method of known samples, is used for hard or
uniform ores where it is difficult to cut channels. In
this method the samples are collected by taking a
small series of chips of rocks on a regular grid pattern
from the working face in regular intervals. The
blasted, broken material are sampled. The shape of
grid is adopted to the morphology and structure of
deposit. The main advantage of this sampling is its
high productivity.

Face or Muck or Lump Sampling
 The term face sampling covers sampling of exposed
faces of ore and waste, this method of taking samples
may be referred to the group of point sampling. One of
three lumps of rocks are gathered in the face are taken
from a pile of broken mineral with the purpose of
finding deforming mineral and also the chemical
composition. It is very simple, quick and cheap
procedure but the accuracy of this method is very low.

Bulk Sampling
 This type sampling method is used in checking of
the reliability of other types of samples and
sometimes may be taken to determine a correction
factor for use in a estimate based on samples of other
types. The samples are taken by blasting down drift
blocks or a section in a stope or otherwise obtaining a
sample of several tons to several hundreds or even
thousands of tons, either from trench, pit ,channelor
from the run-of-mine, where the entire lot is milled
separately .

Drill hole sampling
 This method is more convenient for the determination of
the deposits boundaries. Here samples consists of the
cuttings from drill holes. The samples are usually collected
beyond the walls of underground working with a constant
cross section.
 Drill hole sampling methods:- The methods are classified
based on the type of equipment employed.
Drive pipe method, churn drilling, rotary drilling,
percussion rock drilling (test hole drilling ) etc...
 Planar sampling:- This method is relatively rare
procedure employed on deposits having a very low
content of useful minerals.
e.g.:- pt, Au, cassiterite etc…

Errors in Sampling
 Due to various factor inhert and imposed numerous
errors are possible in the case of sampling and analysis
there are mainly two types of errors. Random and
systematic errors. The errors in sampling is mainly due
to following reasons,
 Improper spacing in samples
 In sufficient number of samples
 Improper location of samples
 Incorrect weighting of assay
 Failure to recognize ore, thus leaving it unsampled.
 Improper chemical analysis and salting

Conclusion
 Sampling is a method of ascertaining the composition
and properties of minerals and establishing their
grade.
 Thus there are many ways to sample and many
methods to calculate the value of a sediment.
 The important concept is that a sample should
represent as closely as possible the value contained in
the material from which it is taken.
 The sampling is useful in almost all the stages of
exploration.

References
Books:
 Elements of prospecting and exploration by
“T.C.Bagchi , D.K.SenGupta, S.V.L.N. Rao”.
(Page :81-96)
 Hand book of petrographic techniques by
“Hutchinson”
Websites:
 www.wikipedia.com
 www.geology.com
 www.google.com

Sampling techniques for mineral deposit

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Sampling techniques for mineral deposit