A Composite Sample in mining geology is a sample that is prepared by physically combining and homogenizing multiple individual samples collected from different locations, depths, time periods, or material types, in order to obtain a single representative sample that reflects the average characteristics of a larger volume of ore, rock, or material. In bauxite, gold, iron ore, and diamond mining, composite sampling is a widely used technique in exploration drilling programs, grade control operations, metallurgical test work, and environmental monitoring. For example, in gold mining, a composite sample may be created by combining chip samples taken at regular intervals from a drill core to represent the average grade of a particular ore zone. In bauxite mining, composite samples from multiple drill holes across a deposit are used to characterize the average alumina content and reactive silica levels of a mining block. In diamond mining, large-volume composite samples are collected and processed through dense media separation plants to determine diamond grade expressed in carats per hundred tonnes. The reliability of composite samples depends on the representativeness of the individual samples from which they are formed, the method of homogenization, and the sub-sampling protocols used to extract analytical portions. Composite sampling must be conducted according to documented sampling protocols and quality assurance/quality control (QA/QC) procedures to ensure that analytical results are accurate and reproducible.
