Some research on geology would provide possible locations for minerals. One such resource for information is Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) now being used to determine what the distribution of matterial on Mars would look like but still the question exists as to why it is so. The planet may have had a cataclysmic impact in the past or there may be seizemic areas where volacnism played a part in distributions and then there is the whole plate techtonic thing we could consider.
The Colony ET project will use a volumetric approach for the actual minerals to be mined and the distribution will be based on the planet type and the landscape. One of the planets we have in operation is volcanic so we are going to base the distribution on that model for both type and location of minerals. Users have to drill down to some unknown level to find minerals then extract them. As the minerals are extracted the volumes decrease and the equipment may need moved to another spot. We think this method will add a bit of realistic uncertainty to the sim.