Prospecting for Gold Veins in Slopes
The work of prospecting for gold in a slope consists in digging small holes or trenches; if the former, they may be spaced some 1.50 to 3.0 m apart, along the base of the slope. The material excavated is washed separately, a record being kept of both location and results obtained. As a rule the occurrences of gold are contiguous, the amount found decreasing in either direction from the productive portion on the line search. The lateral extent of the gold-bearing area having been ascertained, another level some distance up the slope is chosen and is worked as before, except that the center of the area already determined is taken as a center for the new level. By this method of procedure the amount of work done is materially reduced. It is probable that each new level worked will indicate both narrowing of bearing area and an increase in values obtained.
On continuing the operation, the deposits narrows to a point, which is the center of a fan shaped area produced by the downward movement of particles on a slope and under the influence of gravity. The vein is thus located, but it is evident that there are many conditions tending to vitiate the conclusions. If the vein prospected for is spotted in values, as when the pay streak or body occurs at the intersection of veins, in isolated patches or pockets, such a method of procedure may be reliable, provided that the even distribution or spread is not interfered with, but when the whole vein contains values, such extensive and systematic work is hardly necessary as the whole slope should indicate values. Nevertheless, in either case the occurrence of ditches with intervening ridges brings about a concentration of the values along the lines of depressions and if found in the lowest point of the depression it is impossible to determine from which slope it came.
If the vein is spotted as in pocket mines, the work of the gold prospector often proves of no avail for on tracking the wash gold to its source he may find that the supply has been exhausted or only a remnant remains. Other vitiating factors are landslides, which may be old or new; great depth of cover formed subsequent to erosion of the vein; the cutting of gulches; and others. Having located the vein it is considered good practice to extend the work by trenching some distance above in order to ascertain whether other sources of supply lie above. On testing the vein and finding gold, the work of prospecting the vein is just starting. The prospection activity may be difficult due to the presence of dense brush and masses of decayed leaves or trees, and often a covering of moss. With considerable depth of soil, trenches, and shallow shafts may have to be resorted.
The occurrence and appearance of the gold may also be indicative of the presence of the vein from which it was derived. If attached to gangue and rough and porous it has not traveled far, while if flat and worn, it is clear that it is far from its source. The float or shoad rock, sometimes called kindly rocks, consists of portions of the vein-filling, being quartz, calcite, fluorspar.