Lesson 2: Sampling and Sampling Preparation Flashcards
material of volume or quantity manageable for analysis which will represent the tonnage or block of ore reserve to be determined
sample
The process of obtaining such samples
sampling
samples obtained from a large quantity of uniform characteristics are likely ____ or ____ that will determine the composition of the whole mass
true samples or representative
From this, it follows that every determination of value in metallurgy, two (2) distinct operations must be given equal importance
sampling and Chemical Analysis
Primary objective in sampling?
to obtain a representative of a whole mass
metallurgists/assayers are to take a small quantity of the samples obtained from actual mine operations. This new sample must have the same composition as the whole mass where it was taken
sample preparation
dependent on the nature of the material to be sampled
sampling method
In sampling, metallurgical materials may be divided into the following classes:
- Fluids
- Tough or Sectile Materials
- Brittle or Frangible Materials
Ore which breaks into lumps of large variation of sizes are probably of different composition. In such case, ____ the materials into fine powder and thorough mixing is desirable to obtain a true sample.
Crushing
GENERAL PRINCIPLES in Sampling
- For fluids, it is necessary to mix them thoroughly before withdrawing any convenient portion as sample.
- For fragmental materials, quantity to be taken depends upon the value and uniformity of the material and the size of the largest particles
Sample Procedures of the ore
Crushing
VOlume Reduction
Grinding
is a size reduction process and is done to assist the efficiency of mixing the ore samples.
Crushing
After crushing, crushed ores are then thoroughly mixed and reduced in volume through coning and quartering and by using riffles.
Volume Reduction
Samples are shoveled into a conical heap on a sampling flow. The cone is then flattened by drawing the ore from the center outward with the shovel as the sampler walks around the cone. The cone is then quartered and opposite quarters are discarded
Coning and Quartering
equipment used in diving crushed samples into halves.
Riffle
In order to save much time in dissolving ore for analysis, ____ using good mechanical samplers is employed
Grinding
Sampling errors come in two basic types
COntamination and Procedural
occur at any stage in exploration and is a much larger issue for precious metals. For example, a logger logging core with a gold ring on.
Contamination Error
Any redepositing of a metal or material where it isn’t supposed to be is considered
Contamination
errors resulting from deviations from the sampling procedures. Perhaps a sample tag is mixed up or not recorded properly or maybe the core cutter cut the sample improperly, or maybe the lab didn’t mix the sample properly.
Procedural Errors
are materials which are guaranteed not to contain any of the mineral being assayed for. This will determine if potential contamination at the lab setting is taking place.
Blanks
If a known non-mineralized sample shows a positive result to a mineral – a_____ . _____ are usually purchased from labs, or simple ground up glass will suffice.
A RED FLAG IS RAISED
BLANKS
purchased from labs, which have a known grade of mineral to be tested for
Standards
What is the purpose of the standard?
to test for calibration errors at the lab level
A standard which is returned with a value outside the accepted range (given by standard source lab) could indicate ____of the sample, or an ____ of the equipment/personnel handling the samples.
Poor Mixing of the sample, calibration error
secondary splitting of core resulting in two samples that in theory should be similar in grade
Core Duplicates
The second, usually done as _____ in the lab is to retest a sample already tested, again the samples should in theory be similar
Internal tests
Rule of Thumb in duplicates
all samples above a certain grade are automatically re-sampled for verification
