Vein (geology)

“ They seldom exceed a few inches in thickness, and are in general much more slender; the same vein which in the middle is an inch or two in thickness, gradually thins away at each extremity, sometimes to a hair's breadth, at other times shooting of like a spreading root of delicate fibres. ”

“ The veins which pass perpendicularly through limestone beds, acquire an inclination in the alternating shales, and they are usually wider in the limestone than in the shale. Now, in both of these circumstances, the vein fissures resemble common joints, which not uncommonly are more inclined and much narrower in shales, than in the limestone strata of the same district. ”

“ It may be a more or less mineralized sedimentary formation with limits determined by original deposition. It is very often bent or folded, and even more often faulted; the faulting may be of great complexity, making it extremely difficult to follow the vein. The vein may be cut by other veins of different ages, which in places may be hard to distinguish one from another. Erosion working down on a complex vein displaced by faulting and folding may bring several parts of the same vein to the surface, developing what seem to be separate vein apices. ”

“ Their downward direction is seldom quite vertical; there is however a species of vein having also an east and west direction which is never metalliferous, but consists generally of clay; this vein is for the most part found to take a course under-ground much less approaching the perpendicular than the metalliferous veins. This variation from the perpendicular in an east and west vein, whether it be towards the north or south, is called the underlie, and when its direction or dip is opposed to that of the metalliferous vein, it mostly, disturbs the direction of the latter. ”

“ Veins are bounded by walls. The rock in which a vein is found is a country rock. Smooth walls are called "slickensides." The upper wall of an inclined vein is the hanging wall; the other the foot wall. A layer of clay between the veins and wall is a selvage. A mass of rock enclosed in the vein is a horse. The vein stone, or gangue, is all that part of a vein that is not mineral.
A FAULT.
The throw of a fault in a vein is measured by the amount of vertical displacement. ”

“ The radicles of the inferior vena cava and the left posterior cardinal are formed by the renal veins from the two kidneys, and in their forward course to the heart both veins receive in addition genital and segmental veins. In its course through the liver the inferior vena cava receives several hepatic veins, and finally opens into the sinus venosus, while the left posterior cardinal vein joins the corresponding Cuvierian duct, which also receives anterior cardinal, inferior jugular, and subclavian veins. ”

“ These veins are subject, like coal, to be interrupted, broken, and thrown up or down by slips, dykes, or other interruptions of the regular strata. In the case of a metallic vein, a slip often increases the chance of finding more treasure. Such veins do not preserve the parallelism of their beds, characteristic of coal seams; but vary excessively in thickness within a moderate space. Flat veins occur frequently in limestone, either in a horizontal or declining direction. The flat or strata veins open and close, as the rake veins also do. ”

“ In this loose rock and the veins which are by this description readily found and identified, they are about three inches in thickness, and in some places widen out into pockets even a foot in diameter They look like seams of a dark earth, with blotches of white or green matter where they are weathered, but are fresher in appearance inside. The rock, in the immediate vicinity of the veins, is soft, and may be readily broken out with the hammer of, if possible, a pick bar, and thus some of these geode cavities broken into, and much finer specimens obtained than in the vein proper. ”

“ Large masses of mountain are sometimes as full of veins as your hand is; and of veins nearly as fine (only you know a rock vein does not mean a tube, but a crack or cleft) . Now these clefts are mended, usually, with the strongest material the rock can find; and often literally with threads; for the gradually opening rent seems to draw the substance it is filled with into fibers, which cross from one side of it to the other, and are partly crystalline; so that, when the crystals become distinct, the fissure has often exactly the look of a tear, brought together with strong cross stitches. ”

“ The distribution of the veins of the rabbit has only a superficial parallelism with arteries. The chief factors of vena cava inferior are the hepatic vein (h.v.) , which receives the liver blood, the renal veins (r.v.) ”

“ The ancient mode of shoding for tin-veins, consisted in tracing certain stones, of which tin formed a proportion considerable enough to excite attention, and found at or a little below the surface, to the vein from which they had been accidentally detached, so as to have passed in a sort of succession down the side of a hill. Another mode of seeking tin veins is by sinking pits through the superincumbent earth down to the solid rock, and driving a trench from one to another, north and south, so as to meet with every vein in the track through which it passed. ”

“ Nor are the veins equally apparent in all animals; but they are more manifest in [Pg 57] those which have most blood, and in the largest creatures; but in those animals which are small, and have not much blood, either by nature or from excess in fat, they are not so easily investigated, for some of the passages are confused, like rivulets that are lost in beds of mud; and there are some animals which have but few, and these fibres instead of veins. The great vein is very conspicuous in all, even the smallest animals. ”

“ But whatever may be the age of these different parts of the vein, they are all necessarily posterior to the rock of the mountain in which the vein occurs, and in the present case, to the granite and the grauwacke, the only two formations of any extent that are met with in Cornwall and Devonshire.
As the same vein-stones are found in different formations of veins, we must therefore admit, that the same rocks have been held in solution at different periods.
Massive quartz sometimes forms alone the greatest part of the vein-stone of certain veins. ”

“ Some veins run straight along on the plateaux, the hills, or plains. In the next place, venae profundae differ not a little in the manner in which they intersect, since one may cross through a second transversely, or one may cross another one obliquely as if cutting it in two. If a vein which cuts through another principal one obliquely be the harder of the two, it penetrates right through it, just as a wedge of beech or iron can be driven through soft wood by means of a tool. ”

“ The extensive mining operations to which veins have been subjected in all parts of the world, have made our knowledge of their forms below the surface very full and accurate. It has been learned in this way that very often the corresponding portions of the walls of a vein do not coincide in position, but one side is higher or lower than the other, showing that the walls slipped over each other when the fissure was formed or subsequently ”

“ But their disadvantages are numerous; for although the regular metalliferous veins are occasionally found to be but little or not at all disturbed by the passing of the substance of the cross vein through them, except by the mere division of the load, it more often happens that it is as it were broken into small strings or branches. By a careful examination of the nature and direction of these, the miner is indeed sometimes enabled to find pretty readily that part of the load which is on the other side of the cross vein, but he is often baffled. ”

“ Fig. 6.—Venous System of Xenopus and Rana.
[In the Frog the abdominal vein is also formed by the union of the two pelvic veins. The pelvic veins, however, lie more superficially than in the Platana. The femoral vein which passes along the front of the thigh divides into two branches, the one branch forming the pelvic vein, the other, joined by the sciatic vein from the muscles and skin of the back of the thigh, forming the renal portal vein extending along the outer side of the kidney. The dorso-lumbar vein from the dorsal wall of the body joins the renal portal vein.] ”

“ When its underlie is so much quicker than that of the latter, as to overtake it in going down, the metalliferous vein is generally found to increase in size, not merely in the proportion of the addition of the lesser vein, but very much more, so as to make a great body of ore, called by the miner a gulph of ore at their junction. ”

“ Blood then ceases to flow along the allantoic vessels; they become obliterated. The vitelline vein, which as the yolk becomes gradually absorbed proportionately diminishes in size and importance, comes to appear as a mere branch of the portal vein. The ductus venosus becomes obliterated; and hence the whole of the blood coming through the portal vein flows into the substance of the liver, and so by the hepatic veins into the vena cava. ”

“ The distinction between mineral veins and other veins is to a large extent artificial. With improvement of methods of mining and extraction deposits formerly unprofitable become payable, and in all cases veins vary considerably in the amount of ore they carry. The rich parts are sometimes called shcots or bonanzas, while the barren portions are often left standing in the mine. Near the ground surface the vein stones become oxidized and the metallic minerals are represented by oxides, carbonates, hydrates, or in the case of gold and silver veins they may be rich in the metals themselves. ”

“ Some unnecessary doubts appear to have been entertained by geologists respecting the formation of those smaller veins which have their origin and termination in the rock where they are found, and which have no communication from without. ”

“ THE VEINS OF THE NECK Branches of the Vena Jugularis The trunks of the vena jugularis or vena cephalica communis pass subcutaneously on both sides near the trachea and the esophagus. Near the height of the thyroid gland they almost touch the carotid artery. They then cross, dorsalward, the trunk of the subclavian artery, and in their course receive the vertebral vein and unite with the subclavian vein toward the side of the vena brachiocephalica. The union on the right side lies to the right of the anterior aorta, and the union on the left side lies to the left of the pulmonary artery. ”

“ Many valuable minerals are found in veins running through rock. Veins can be formed when: (a) mineral-laden ground water seeps into cracks, evaporates, and leaves mineral grains that build up into a vein; (b) hot water from deep within the earth fills cracks, then cools and deposits much of the material in solution as minerals in a vein—sometimes including metals such as gold and silver; (c) molten gaseous material squeezes into cracks near the earth's surface, then slowly hardens into a vein. ”

“ Veins are hollow and round, like pipes, arising from the liver, carrying blood and natural spirits; they feed all the parts. Of these there be two chief, Vena porta and Vena cava, from which the rest are corrivated. That Vena porta is a vein coming from the concave of the liver, and receiving those mesaraical veins, by whom he takes the chylus from the stomach and guts, and conveys it to the liver. The other derives blood from the liver to nourish all the other dispersed members. The branches of that Vena porta are the mesaraical and haemorrhoids. ”

“ In the rabbit a vein is a vessel bringing blood towards the heart, while an artery is a vessel conducting it away. Veins are thin-walled, and therefore flabby, a conspicuous purple when full of blood, and when empty through bleeding and collapsed sometimes difficult to make out in dissection. They are formed by the union of lesser factors. The portal breaks up into lesser branches within the liver. Arteries have thick muscular and elastic walls, thick enough to prevent the blood showing through, and are therefore pale pink or white and keep their round shape. ”

“ The cutaneous and the muscular veins, lying under the pectoralis muscle, and arising independently from the subclavian vein. They supply the skin and muscles in the region of the arm. There is a second cutaneous vein arising from the abdominal vein and extending on to the skin of the abdomen. Two other small cutaneous veins are seen on the skin of the leg, and another on the skin under the mouth.
[In the Frog a single musculo-cutaneous vein is seen lying under the pectoralis muscle and extends on to the skin.] ”

“ There may be other reasons in addition; but this is obvious and important, and agrees with an opinion of those countries, which affirms that veins of small amount of dislocation (or "throw" as it is called) are, on the whole, more regularly productive than those attended by enormous displacement. (See Forster and Sopwith on the Veins of Aldstone Moor; and Geology of Yorkshire, vol. ii.)
In Cornwall, some veins bear tin or copper both in granite and killas; others yield more in one of these rocks; the veins are also very unequal in their produce in relation to depth from the surface ”

“ When tin ore is intimately mingled with quartz and chlorite, the vein is termed a scovan load, which is of a dark brown or of a greenish hue, but not very hard, or compact. A load of this description rarely exceeds 12 or 14 inches in width, but it sometimes occurs in a vein the contents of which are not solid, thence by the miners termed a sucked stone. A load so circumstanced is often several feet wide. ”