The location of the shaft for gold exploration whether vertical or inclined, is also of considerable importance, and not only from the standpoint of ease sinking and stability, but in regard to the methods of handling the mine product. When a vertical shaft is located on the outcrop of a pitching seam, it is evident that the line of the shaft will soon deviate from the course of the vein, thus necessitating the driving of cross-cuts, both above and below the intersection of the shaft with the vein. Further, with due regards for other controlling factors, the distance of the shaft from the vein outcrop, must bear a definite relation to the proposed depth of the shaft or development of the property.
Inclined shafts are usually sunk in the vein for several reasons, the more important being ease of sinking, as the vein-filling is usually softer and more easily worked than the country-rock, and the value as means of ascertaining the extent and character of the deposit. Nevertheless, when in the vein, more care must be taken in the support of the excavation, which involves the leaving of pillars of mineral standing in the vein, and the consequent reduction of the percentage of extraction. The loss of mineral may be largely overcome by sinking the shaft in the foot-wall, although the advantage of sinking in the vein material is largely offset, but the inclined still has the advantage over the vertical shafts, in that the length of cross-cuts is considerably less.
Basically, shafts should be located in the foot, rather than the hanging wall owing the fact that there is less danger of movement. Further, to prevent reversing the grade or direction of hoisting, when inclined shafts are employed, it is necessary to place the ore bins and surface works on the foot-wall of the outcrop. The consideration outlined above may be considerably modified by prevailing conditions, such as fissuring and faulting of the vein, and its intersection with one or more productive or non-productive veins. Having made connections between the surface and vein by means of shafts and cross-cuts, levels are formed in the vein by driving drifts at the points of intersection of cross-cuts or shafts with the vein. The levels are in turn connected by other opening the vein, which according the whether they are sunk or driven upward, are called winzes and raises. The secondary connecting passages are usually spaced at more or less regular intervals along the line of the levels, and on either side of the shafts.
Beginning with the levels, their roofs are attacked, which work is continued upward until the level above is reached. The process of removing the valuable portion of the vein lying between levels is known as stoping, being designated as over and under hand stoping, according to whether the work is done by breaking down the roof or heaving up the floor.