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The face of each wall of the fissure is often beautifully polished, as if glazed, striated, or scored with parallel furrows and ridges, such as would be produced by the continued rubbing together of surfaces of unequal hardness. These polished surfaces are called by miners "slickensides." It is supposed that the lines of the striae indicate the direction in which the rocks were moved.
He remarks that similar breccias with slickensides are observed on a minor scale where rocks of different composition and rigidity are contorted together. Such protrusion may have been brought about by degrees by innumerable shocks of earthquakes repeated after long intervals of time along the same tract of country.
SLICKENSIDES. If we examine the walls of a fault, we may find further evidence of movement in the fact that the surfaces are polished and grooved by the enormous friction which they have suffered as they have ground one upon the other. These appearances, called sliekensides, have sometimes been mistaken for the results of glacial action.
Bedded veins may be distinguished from fissure veins by the absence of all traces of a fissure, the want of a banded structure, slickensides, selvages, etc.; from gash veins and the floors of ore which often accompany them, as well as from segregated veins, they are distinguished by the nature of the inclosing rock and the foreign origin of the ore.
The fawn-grey colour, here shining as if polished by "slickensides," there dull and roughened by the rude touch of Time, is a neutral ground that takes all the tints with which sun and moon, mist and cloud, paint and glaze the world: changeable as the chameleon's, the coating is never the same for two brief hours.
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