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OF SOUTH CAROLINA. . 15 
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Merauuic VEINS. 
Veins being cracks or fissures in rocks, filled with mineral matter, their analogy with dykes is 
quite obvious. When the mineral matter is a metal the veins are called metallic veins. The whole 
substance of the vein is, however, rarely composed of a metal: in that case, the mineral with which 
the metal is combined is called the gangue, and the whole metalliferous vein the lode. The 
rock which contains the vein is called, in mining phraseology, the country. Veins occur of all 
sizes, from the thickness of a mere thread to that of many fathoms; nor does there appear to be any 
connection between the thickness and relative productiveness of veins, although it often happens 
that when a very thick vein contracts its dimensions, it is found comparatively richer. 
The passage of a vein from one rock to another is often marked by a corresponding change in 
productiveness. It is a common impression among the miners in South Carolina, that gold veins 
become richer when they pass from a soft to a harder rock. But this difference is still greater at or 
near the point of contact of the igneous and metamorphic rocks. 
Metalliferous veins are regarded as contemporaneous with the strata in which they are found— 
when they are completely enclosed in them, forming irregular masses of limited extent, and 
generally differing but little in appearance from the rest of the rock. When the veins intersect the 
strata they are, of course, posterior to them, and are generally very distinctly separated from the 
rock in which they occur, by smooth walls. Such are called true veins, and are designated by 
English miners as rake veins, when they cut the strata either perpendicularly or inclined, and 
descend to a great depth in the earth. ‘The course or bearing of rake veins is generally straight. 
Pipe veins are large, irregular masses, that seem to push themselves, like wedges, between the 
strata, and have sometimes the appearance of beds—their inclination depending frequently on the 
dip of the rocks. £laé veins are generally horizontal, and seem to be openings between the strata, 
filled with metalliferous matter. Such veins are subject to frequent dislocations and disturbances. 
Interlaced masses are portions of the rock or country, intersected in all directions by veins, 
forming a sort of net-work. 
East and West lodes are metalliferous veins, whose direction or bearing does not vary more than 
30° from these points. 
When a series of such veins is intersected by other veins, nearly at right angles, the latter are 
called cross courses. The dislocations that take place at such intersections are often sources of 
great difficulty to miners. The continuity of the veins is broken. The derangement thus pro- 
duced is called a faulé or shift, and the distance to which the vein is thrown from its bearing is 
ealled the offeast. In coal mines, such dislocations are a source of great difficulty to the miners. 
Very often, when they are pursuing a seam of coal with great success, it is suddenly cut off, and 
recovered with much labor and delay. When a fault occurs it becomes, therefore, a matter of great 
interest todetermine on which side the offcast takes place; or, in other words, on which side we 
are to look for the lost vein. 
In the mines of Saxony and Cornwall it is considera as established, as a general law, that the 
offcast takes place on the side on which the obtuse angle occurs. For example, if the vein a6, Fig. 
6, be dislocated by the intersection of the cross course, ¢ d, we must search for the lost vein, e, on 
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