Gold deposits are located in places whose Lithology or rock formation is variable and the importance of rock types is an significant consideration when it is important to classify and detect gold deposits. Basically, it is important to recognize rocks at sight, when they are picked up or clearly defined in a cliff. When travelling over the mountains, a gold prospector surveys the grand panorama from the top and it is important to identify peculiar forms and patterns each variety of rock is apt to take as the results of erosion and weathering owing to different degrees of hardness, to be able to make a classification considering if the main rock is granite, limestone or porphyry.
It is important to mention that rock formations and the character of distant rocks indicate the possible formation of the gold deposit and the future implications on the development of models for the ore body. In sharp granite, it is possible to find fissure veins. Distant cones like the spires and minarets indicate porphyry or igneous rocks, another mark where they break through the sedimentary strata. It is possible to observe grassy slopes, which probably are underlaid by sandstone or limestone. In some gold deposits is possible to recognize granite basis and on top a series of sedimentary rocks. The lowest of these, by its rusty white, masonry structure is synonym of quartzite with thin bedded strata.
Some rock formations running in and out irregularly among strata, sometimes between the stratification planes, at others cutting across them make reference to intrusive sheet of porphyry and looks as a contact deposit. Basically, a rock running up like a low wall from the bottom of the canyon to the top may be either a quartz fissure vein or a porphyry dyke.
There are several ways of studying rocks, one by hand specimens, finding out all the minerals composing them and then identifying the minerals composing them and the rocks from which they came. Another aspect is to observe the appearance of large masses of rocks in the field and much their mode of occurrence. It is important to be accurate, microscopic sections may be studied later. It is important to know the most important rocks, which are probably metamorphic and igneous. Nearly all sedimentary rocks, except limestone, are derived from fragments of igneous and metamorphic rocks. According to some prospectors most sedimentary rocks are derived from granite alone and the remainder from the igneous rocks. Essentially by describing the parent rock, the derivate one is more easily determined. Only by knowing what types of rocks are present in gold deposits, it is possible to evaluate the economics of any project, and importantly, search for more gold ore.