Mineral vein

“ Ore-veins, however, are almost always nearly vertical; so that boring is of little use, as it might pass by the richest vein, or, striking it lengthwise, give a too favorable result.
As heavy minerals do not drift far, metals are always found near their source.
Horizontal beds can be worked at the least cost.
Pockets and nodules, or any detached masses of minerals, are soon exhausted. Veins, lodes and beds are most valuable.{83}
Boring a three-inch hole, which costs about $1 a foot, is a good method of testing a mineral vein or bed which lies more or less horizontally. ”

“ When a vein is composed of a single mineral, as quartz, it may rival a dike in its homogeneity. Most important veins, however, are composed of several or a large number of minerals, which may be sometimes more or less uniformly mixed with each other, but are usually distributed in the fissure in a very irregular manner. The great granite veins which are worked for mica, feldspar and quartz, are good illustrations, on a large scale, of the structure of veins in which several minerals have been deposited cotemporaneously. ”

“ That mineral veins have been filled with matter in a fluid state, is acknowledged by every body who has either looked at a mineral vein in the earth, or in a cabinet specimen; mineralists and geologists, in general, suppose this to have been done by means of solutions and concretions, a supposition by no means warranted by appearances, which, on the contrary, in general demonstrate that the materials of those veins had been introduced in the fluid state of fusion. ”

“ Chemical Deposits in Veins.—If we now turn from the mechanical to the chemical agencies which have been instrumental in the production of mineral veins, it may be remarked that those parts of fissures which were choked up with the ruins of fractured rocks must always have been filled with water; and almost every vein has probably been the channel by which hot springs, so common in countries of volcanoes and earthquakes, have made their way to the surface. ”

“ 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. ”

“ It is a proposition requiring no argument that if by the aid of mineral bearing solutions the ores occurring in veins are to be enriched, these solutions must enter the veins. And if all the meteoric waters which fall upon the outcrop of a vein or upon rocks containing disseminated ore run off rapidly down the mountainside without remaining to oxidize, dissolve and penetrate the vein with their load of mineral, there can not be any enrichment caused thereby. ”

“ If the miners find no stringers or veins in the hangingwall or footwall of the main vein, and if they do not find much ore, it is not worth while to undertake the labour of sinking another shaft. Nor ought a shaft to be sunk where a vein is divided into two or three parts, unless the indications are satisfactory that those parts may be united and joined together a little later. Further, it is a bad indication for a vein rich in mineral to bend and turn hither and thither, for unless it goes down again into the ground vertically or inclined, as it first began, it produces no more metal ”

“ The mineral veins, particularly those that yield copper and tin, run nearly from east to west, having the same direction with the beds of the rock itself, which is a very hard schistus. The granite lodes, as also those of porphyry, called elvan in Cornwall, are at right angles nearly to the former; and it is remarked, that they generally heave the mineral veins, but that the mineral veins seldom or never heave the cross-veins. In this country, therefore, the veins of granite and porphyry are posterior in formation to the metallic veins. ”

“ Faults often occur, moreover, in connexion with eruptive outbreaks, and therefore in circumstances especially favourable to ore deposition. From all these reasons it is not surprising that the “true fissure vein” based on a profound fault has been the ideal of the prospector’s search in many parts of the world, and has often been his reward. The historic veins of Cornwall and of Saxony are of this type, also the great silver veins of Mexico, the gold veins of California, the great silver-gold deposits of the Comstock lode, and many in South America. ”

“ On different kinds of mineral veins.—Every geologist is familiarly acquainted with those veins of quartz which abound in hypogene strata, forming lenticular masses of limited extent. They are sometimes observed, also, in sandstones and shales. Veins of carbonate of lime are equally common in fossiliferous rocks, especially in limestones. Such veins appear to have once been chinks or small cavities, caused, like cracks in clay, by the shrinking of the mass, which has consolidated from a fluid state, or has simply contracted its dimensions in passing from a higher to a lower temperature. ”

“ To the suggestion that giving this construction to the bond and conveyance is in effect the granting of a section of a vein of mineral, the answer is that there is nothing impractical or unnatural in such a conveyance. It does not operate to transfer the vein in toto, but simply carves out from the vein the section between the vertical side lines of the ground, and transfers that to the grantee. The title to the balance of the vein remains undisturbed. ”

“ The counsel for the Mammoth Company contends that the supreme court of Utah based its judgment upon assays and a definition that fails to recognize that a vein may be a vein, although it is in soft rock, like limestone, where the walls of the fissures have been eaten into by the mineralizing solutions, and although the surface water has leached the valuable mineral constituents from the upper portion down into the vein. ”

“ 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. ”

“ Phlozopite.--In a vein near the lower end of the quarry, near the asbestos locality, occurs large plates of this mineral, which is a variety of mica, and has all of the characteristics of a pure silvery white color, and from one by three inches in area to less. It is easily separable in folia, and cannot be confounded with any of the other minerals. A huge mass of the veinstone holding abundance of this mineral is exposed, whence it may be plentifully obtained in excellent crystals. ”

“ THE unstratified minerals exist either in veins, intersecting the stratified, or in masses surrounded by them. Veins are of various kinds, and may in general be defined, separations in the continuity of a rock, of a determinate width, but extending indefinitely in length and depth, and filled with mineral substances, different from the rock itself. The mineral veins, strictly so called, are those filled with crystallized substances, and containing the metallic ores. ”

“ Veins are the fillings of cracks or fissures in rock. The filling is generally accomplished through the agency of underground water, which dissolved the mineral matter from the rock, brought it to the fissures and there deposited it. Veins are called mineral veins or, often, lodes, if the material is valuable for commercial purposes. ”

“ On no part of the history of veins has observation pronounced a more positive decision, than on the relation borne by their distribution to physical geography. The truth is universally recognised, that while extensive plain countries are utterly deprived of all indications of these valuable mineral deposits, and others contain them but rarely and in small quantity, there are few mountain countries in which mineral veins are not found in abundance and variety. ”

“ Another effort to penetrate the mystery of metallic depositions, was that of Werner, who, in 1791, gave what he considered a "New Theory of Mineral Veins," of which the principal points of novelty are, the application of the phenomena of intersections to determine the ages of veins, and the hypothesis of aqueous solution for the filling of the fissures. ”

“ For we know that the rents in which ores abound extend downward to vast depths, where the temperature of the interior of the earth is more elevated. We also know that mineral veins are most metalliferous near the contact of Plutonic and stratified formations, especially where the former send veins into the latter, a circumstance which indicates an original proximity of veins at their inferior extremity to igneous and heated rocks. ”

“ Advantageous Effect of Disturbing Forces in giving Origin to Mineral Veins. [1]
A further result attending the Disturbances of the surface of the Earth has been, to produce Rents or Fissures in the Rocks which have been subjected to these violent movements, and to convert them into receptacles of metallic ores, accessible by the labours of man. The greater part of metalliferous veins originated in enormous cracks and crevices, penetrating irregularly and obliquely downwards to an unknown depth, and resembling the rents and chasms which are produced by modern Earthquakes. ”

“ The spars and veinstones which are thrown out in the rubbish of our mines, may be as precious in the eyes of nature, as conducive to the great objects of her economy, and are certainly as characteristic of mineral veins, as the ores of silver or gold, to which we attach so great a value. ”

“ The third reason for supposing those mountains primitive, is taken from the metallic veins, which are found so plentifully in these masses. Now, had these masses been the only bodies in this earth in which those mineral veins were found, there might be some species of reason for drawing the conclusion, which is here formed by our philosopher. But nothing is so common (at least in England) as mineral veins in the strata of the latest formation, and in those which are principally formed of marine productions ”

“ The alteration of felspar into kaolin or china clay is also a pneumatolytic process. and is often found along with tin veins or other types of mineral deposit; probably both fluorine and carbonic acid operated in this instance along with water. Equally common and important is the silicification of rocks near mineral veins which carry gold, copper, lead and other metals. Granites and felsites may be converted into hard cherty masses of silica. ”

“ The immense violence which has accompanied the formation of mineral veins, is particularly marked by the slips and shifts of the strata on each side of them all tending to show what mighty changes have taken place in those regions, which our imagination erroneously paints as the abode of everlasting silence and rest. This shifting of the strata is best observed, where the veins make a transverse section of beds of rock, considerably inclined to the horizon. ”

“ In few metalliferous veins does the ore prove so continuous, as after it has been taken away to leave a large hollow load. The intermediate spaces between the ore are mostly filled with what the miner terms deads, which consist of quartz, fluor, gossan, iron pyrites and other substances, as well as occasionally portions of the country through which the vein runs; but the walls of the vein are nevertheless generally determinable. The deads are not always a disadvantage to the miner, as they serve to keep apart the country on either side the vein ”

“ The gangue of these veins is generally quartz, either pure, or mixed with green particles analogous to chlorite. They contain iron pyrites, blende, sulphuret, and several other compounds of copper, such as the carbonate, phosphate, arseniate, muriate, &c. The most part of the copper veins are accompanied with small argillaceous veins, called by the miners fluckan of the lode. These are often found upon both sides of the vein, so as to form cheeks or salebandes.
When two veins intersect each other, the direction of the one thrown out becomes an object of interest to the miner and geologist. ”

“ 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. ”

“ 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. ”