Riffle splitter
The riffle splitter is a static and fractional sub-sampling device that can be used for dividing a lot of dry particulate material into two half-lots. The device is usually constructed with steel sheet and should be designed to have an even number of opposing inclined chutes (the riffles), with each chute having the same width. The recommended chute width should be at least 2.5× the size of the maximum particle diameter that can be found in the lot to be split. Riffle splitters are typically used in assay and analytical laboratories to reduce the size of  samples provided from other sources (crushed rock, soils, powders and so on) to a lot size that is appropriate for the next stage of analytical sample preparation. Design. There are many different versions of the riffle splitter. However, not all can be considered correct sub-sampling devices, in that the two sub-sample halves are deemed to be representative of the original lot. The issue of correctness of a riffles split sub-sample are function of both the design and the use of the splitter. The design key items are: Use. Incorrect use of a riffle splitter will lead to  sample biases, with the subs lot potentially having unacceptably higher or lower concentrations of the lot analytes or attributes being measured. The main operational factors are as follows: Use in mineral exploration. In many real-world situations outside the laboratory obeying the correct use advice above is not always possible. In particular tiered riffle splitters are widely used in the mineral industry for sub sampling drill hole cuttings at the drilling site. These devices are problematic in that they are usually fed rapidly, the dump-devices are not well designed to allow the material to flow evenly and freely, and  the volume of material and sometimes moist state, often results, in choking of the splitter, overflows and sample losses. The best approach is usually to slow the rate of drilling, split the primary lot after drilling as a separate exercise (not part of the drilling routine) and only split samples that are dry and free flowing (all other need be dried and crushed). Importantly replicates samples from the splitter rejects need to be collected regularly to monitor the potential splitter bias that may occur when the analytical sub sample is always collected from the same side of the splitting device