Recognition of Rock Joints
It is important to indicate that joints, common to rock formation are formed by shrinkage of rocks in passing from soft matter or muddy condition to one consolidation. The effect of faulting is partial. A fissure vein, even in granite series, seems to occupy extensive joint cracks rather than fault planes. These may be due to the shrinkage of the whole mountain mass in consolidating from a semi plastic or aqueous-igneous state of softening to one more consolidated and rigid. For example, the joints in lava sheets forming especial columns due to shrinkage from a molten condition. Such joints may sometimes be mineralized with gold bearing minerals for a short depth forming gash veins rather than fissure veins.
The joints in sedimentary rocks are due to consolidation from a soft, muddy, incoherent condition; such joints may similarly be occupied by gash veins or may lead to pockets or wide blanket deposits. Basically, the line of weakness between one stratum and one set of strata and another, often a favorite line for blanket deposits is due to one stratum being first laid down and partially consolidated before the next. Rocks made up of loose rocks such as porous sandstones and conglomerates are permeated by ore solutions. Sandstones are usually impregnated with iron and copper stains. It is possible that some orebodies were deposited from aqueous solutions and as a consequence, the rocks acquired some texture and structure for this process.
In some joints, the appearance of veins from little distance is that of broad yellow stains of iron oxide, which may have a contrast with some rocks. Also, the quartz due to its hardness stands up above softer lava like a low, rusty or white wall. In some places, the vein is represented by a sharp, shallow, depression forming a narrow little trench. In this case, the vein has decomposable minerals such pyrite and its oxidation decomposition products were washed out leaving a depression in the rocks. For this reason it is important to observe and study brown stains, quartz veins, gulch and the path of a creek.
It has been detected that some fragments that have fallen into an open fissure gradually filling up with solutions of quartz and vain matter in which they are present, but rather some fragments of the wall rock. The shadowy outlines of fragments may be observed partially but not completely replaced by quartz or vein compounds. Also, the joints present some characteristics or properties that help to identify some rock properties of gold deposits.
Some rock joints may be mineralized with gold bearing minerals