If the sample is large and the coning and quartering method was used for blending, normally one half or three quarters of the sample is split out and reserve for future use. In this way the coning and quartering method is repeated on the sample to reduce the weight to give sufficient sample for the testing program. The Jones riffle is used to split the sample to approximately 1 kg. These portions are transferred to plastic bags; one portion is taken at random and placed on the rubber mat and mixed several times. Having tared the weigh scales with an empty plastic bag, each sample is weighed to exactly 1 kg. Using a spatula add material from the mat or conversely if the sample weight is more than 1 kg, carefully remove the required quantity. Finally, seal and label each test bag. Samples must be stored in a clean, cool and dry place. If the sample contains high sulphides, the samples should be kept in a freezer to avoid oxidation (aging).
For samples larger than 10 kg, one kilogram is selected at random as the head sample. A 250 gram portion is removed by riffling. This portion is pulverized to minus 100 mesh, mixed on a rubber mat and approximately 30 g removed by scoop for chemical analysis. The remainder of the pulverized sample is stored for future reference.
Now, the next step is to get a representative sample for chemical and physical assays. For samples less than 10 kg, the head sample should be riffle out at the time of sample preparation for laboratory work. Do not use leftovers after the test charges have been prepared as this portion could be seriously biased. A 250 gram portion is removed by riffling. This portion is pulverized to minus 100 mesh, mixed on a rubber mat and approximately 30 g removed by scoop for chemical analysis. The remainder of the pulverized sample is stored for future reference. A smaller amount than 250 g is acceptable as a head sample if the overall sample weight is limited.
Any contamination of the sample will result in false test data being obtained. It is important to make efforts in order to assure that the work area and equipment are clean prior to employ and between different samples are prepared for test work programs.
