There are two types of samples to be studied. The first group is formed by the grab samples taken at the beginning of the project. These samples are basically rock chips. These samples must be bagged and sent to the lab for assays and metallurgical tests. The second group is constituted by cores from drill holes, cut channel samples or bulk samples from trenches, or underground workings. Similarly to the first group, the samples need to be assayed and tested metallurgically. For assays, these samples must be reduced in volume and size of particles without dilution or enrichment of metal values.
Samples must have specific codes
Field samples are sent to the sample preparation facility where the samples will be divided for geology and metallurgical information. In order to deliver the sample in the best condition to the laboratory facility is necessary to consider some factors such as use appropriate labels and names to identify the samples, define the procedure to be employed for bagging and sample collection, assure the sample preservation, manipulate the sample when is necessary, and minimize the movement of the sample in and out of the container. The storage and transportation must consider the oxidation conditions to be exposed the samples and more even if the presence of sulphides is important. Under this consideration, samples must be stored in a freezer. If the samples need to be logged and cut, they must be taken from the freezer. When the samples have to travel a long distance is good practice to wrap the samples in a bag which air was purged with nitrogen. In this way the sample will stay in inert atmosphere and the possible risk of oxidation will be minimized.
Cores must be stored and transported in boxes
Normally, drill core samples are split in half with a diamond core saw. One half is submitted for analysis and/ore metallurgical tests and the other half is stored. The core has to be photographed at the site, geologically logged and geotechnically logged. The core samples are selected by the geologist based on logging information and must be labelled with the right code and name. Samples range in length from 0.20 m to 2.5 m and their weight is variable, 1.5 to 6.0 kilos. The half core samples are bagged and placed in sacks, security sealed and shipped to the laboratory for sample preparation according to the testwork program.