Sampling techniques for mineral deposit

Sampling techniques for mineral deposit

1. SAMPLING TECHNIQUES FOR MINERAL DEPOSIT

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

3. I ntroduction 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”.

4. 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.

5. 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……

6. 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 .

7. 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)

8. 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 .

9. 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

10. 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)

11. 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.

12. 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.

13. 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 .

14. 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.

15. 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.

16. 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 .

17. 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…

18. E rrors 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

19. 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.

20. 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

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