Sample Reduction

In many cases the sample taken is too much in volume to be sent to the analysis laboratory. In these cases, it will be necessary to reduce it in size, but it needs to be done in such a way that the reduced sample is identical (or where there is hardly any difference) to the original sample. The simplest sampling reductor consists of a brass cross to divide the big amount of the sample into four equal parts. Usually the sample divisor is used that consists of a metal box divided in two by holes that alternately separate the material from one part and the other. The sample that is obtained will be of a few hundred grams and will be sent to the laboratory for the analysis. If the transport costs are cheap, the rest of the samples can be kept for eventual future analysis or to pan wash them. It is very important to wash the divider with a brush after each sampling in order to avoid possible contaminations.

Grinding and sifting
In this case the quarter will be continued until obtaining 50 grams of the sample that will then be ground and sifted without leaving any residue. The particle sizing to be obtained will depend on the type of analysis (40 microns for a quantimetric analysis and 80 microns for wet chemical, atomic absorption and spectrometric emission). It will be necessary to not grind the softer parts too much; therefore sifting needs to be done frequently. It is also necessary to wash the pan when passing one sample to another with a brush.

Wells
These are small study and sampling wells that come about in tabular horizontal deposits or sub horizontal ones. These can be isolated or disposed with square or rectangular netting depending on the prospection and the type of indicator. These are normally excavated by hand, from 0.70 to 0.80 meters in diameter in where the sampling is done by vertical holes in the walls or in the earth by a depth of one meter or of 50 cm as well. In the first case the working will be done as previously described; in the second case, (in the case of homogenous minerals of Fe or Mn), the metric amounts will be placed in a spiral around the well and numbered with landmarks and cards, indicating the number of the well and the depth. In this case the reduction of the sample will be done as described, with the difference that the grinding, due to the large amount, will preferably be done with a jaw crusher that works with a gasoline motor.

Drilling with perforators
For the indication or deposits of certain plastic and soft substances, such as talc, a light perforator is used and which is capable of taking samples up to 15 meters in depth.