Gold vein deposits may present fissure veins, which are usually may be filling of fault cracks and the fissures are mainly due to faulting. Recognition of faults is a very important part of the field work done by a gold prospector. Faulting is the result of extreme folding. In entering a mountain region by way perhaps of a canyon, cutting right through it on the exposed face of the cliff, it is possible to observe some folds, low gentle at first, but gradually as the zone is examined, they are increased in sharpness, steepness and closeness. Basically, the presence of faults may be indicated by a little depression in the outline of the hill or by a line of rubbish and broken rock descending the face of the cliff. In some cases, by a zone of exuberant vegetation.
In general, it is possible to note a fractured tendency of rocks as they approach the fault line. By closer search, it is clear to observe pieces of rock polished or slickensided by the movement of walls of the fault slipping upon one another. Basically, slickenside is a sure proof of motion having taken place in the rocks, and it is often observed on the walls of fissure veins. It has been noted that a gold faulted region is often marked by a step like out-line, each step representing the fallen or risen side of a fault zone. Also, these fault lines must be carefully observed for gold presence, especially if the fault line is occupied by a dyke or quartz vein. In some circumstances, these faults totally show quartz, veinstone or any mineralization. They may be filled up with clay, rubbish and broken rock.
It is important to mention that faulting in some places occurred after the period most marked by deposit of mineral solutions and ore deposits. In this case, the fissures may be occupied by hot or mineral springs making gold veins. Along the face of a canyon wall a gold prospector may notice some peculiar stratum near the top of the cliff and its counterpart out of place near the bottom, showing that a fault is present and its slip may be estimated, but when a fault of many thousands of meters is present, a knowledge of the different geological periods involved in the slip is necessary to estimate the fault.
Faults have their points of maximum depth and disturbance from which they are to disappear at either end in folds or rounded hills. According to some gold prospectors, great faults are accompanied by minor parallel and cross faults. The strain produced by cooling and contraction of the earth are very important causes of fractures. The contraction develops a tangential strain that is resisted by the disposition of the crust. If there is no sufficient support, gravity causes a displacement of the material into folds. If tangential strain is greater than the ability of the rock to resist, they are crumpled into folds.