Experienced gold prospectors and geologists consider that a very important aspect to study a gold deposit is the topography and its relationship with the faults. Basically, the importance relies in the fact that the more recent a fault, and the greater the difference in resistance to erosion between the rocks of its walls, the more likely is it to find expression in the topography; a fault of great displacement that finds no expression in the topography is probably not of recent origin.
Faults may in some cases be recognized at the surface by features other than the lack of correspondence between their walls, such as a fault scarp, a saddle in a ridge, or the course of a canyon, or through the outcropping of a fault breccia that has become silicified and so rendered resistant to erosion. In most cases, however, erosion is the dominant feature in controlling the topography, and structural features are rarely represented at the surface, except through relative resistance to erosion.
It is important to mention that the surface of a gold deposit affords a complete section of the geological features of any district, and in all but the simplest occurrences a geological map of the surface and a few vertical sections are invaluable guides in the examination or exploration of any district. All significant outcrops of rocks, dikes, beds, veins, faults, shear zones and so forth should be determined and their strikes, dips, and elevations recorded on a large scale map, from which the data may be referred for study to a horizontal plane. Contour maps are useful in such work, but in most cases the expense of contouring is not justified, and the elevation of significant readings will be found to be sufficient.
Also, a horizontal section thus prepared, with, perhaps, several vertical sections, will indicate through lack of correspondence of strata or other criteria, the existence and location of faults that otherwise might not be suspected. If the surface observations are abundant, they often give data from which the displacements of faults may be calculated. A geological map of the surface results in dividing a district into fault blocks, conditions within each of which may be considered as constant, but which must be expected to change upon passing from one fault block to another. The importance of dividing a district into fault blocks will be appreciated on considering that a gold prospect may be situated within a few hundred meters of an important mine, but actually separated from it, perhaps, by a fault thousands of feet in throw, or in a formation that is apparently similar, although actually unrelated, to the ore-bearing rock.