Density of the Samples

The density of the samples varies according to the prospection scale and according to the dimensions of the looked for targets. In a strategic prospection a variable scale between 1:200.000 and 1:50.00 is usually worked on. The sampling is done with wide meshes that have a variable density between 1 to some sample of km2, if working on stream sediments. It is always better to talk about the average density than the distance between samples because it gives a more precise idea of the work that needs to be developed. In the tactical phases the density will not be talked about any more but rather the mesh. This will vary in function of the deposit that is being searched for. For example for the first localization of the abnormalities of Pb, Zn or Cu, a first mesh of 200 x 200 meters is enough, but in cases of abnormalities of Sb or W it will be necessary to choose a mesh of 50 x 50 meters.

Analysis
Analysis is one of the punctual points, in reality the choice of a technique to another is able to completely change the efficiency of meaning of a campaign. The technique that is used needs to be contemporarily sensible, reproducible (where it can be used a repeated amount of times always in the same way) and that is not expensive. Essentially there are two strategies that can be used:

• To adopt simple and usable methods also for the terrain, for example in a van that has been adapted into a laboratory;
• Choose a more sophisticated technique, available in a central laboratory (the one most used).

In the tactical prospection phase the problem is defined much better than in the strategic prospection in that only a little group of elements will be analyzed even if certain elements are not directly looked for, they are very useful for evaluating the type of abnormality. For example, Ni will be systematically analyzed in a tactical prospection by Cu, as well as Au, Ag, Mo, Cd, and are interesting indicators for a prospection of Pb and Zn. In the phase of the study of indications and particularly if it is about studying the main aureoles through rock geochemistry, of the multi element analysis they will be indispensable to also visualize the polarity and amount of erosion of a deposit.