Mineral spring

“ During the slow upheaval and denudation of the lodes, they have been subjected to various chemical, hydro-thermal, and aqueous agencies, by which many of their contents have been re-arranged and re-formed, new minerals have been brought in by percolation of water from the surrounding rocks, and possibly some of the original contents have been carried out by mineral springs rising through the lines of fissures which are not completely sealed by the igneous injection, as the contraction of the molten matter in cooling has left cracks and crevices through which water readily passes. ”

“ We know that every volcano and every lava flow must be connected below the surface with a dike; and it is almost equally certain that the waters of mineral springs forming tufaceous mineral deposits on the surface, as in the geyser districts, also deposit a portion of the dissolved minerals on the walls of the subterranean channels, which are thus being gradually filled up and converted into mineral veins, which will be exposed on the surface when erosion has removed the tufaceous overflow. ”

“ But, besides the transfer of matter by running water from the continents to the ocean, there is a constant transportation from below upwards, by mineral springs and volcanic vents. As mountain masses are, in the course of ages, created by the pouring forth of successive streams of lava, so stratified rocks, of great extent, originate from the deposition of carbonate of lime, and other mineral ingredients, with which springs are impregnated. ”

“ As to our mineral springs, they are like the stars for multitude, presenting every variety. Some of our thermal springs, for example the hot, vaporous sulphur caves of Glenwood, Colorado, are constantly demonstrating their restorative efficiency. ”

“ Arago proved that the temperature of the springs corresponds with the depth from which they rise. Bergman, Berzelius, Bischof, and Struve showed that their composition depends on the amount of carbonic acid and other gases which are dissolved in them, consequent on their volcanic origin and on the nature of the rocks which they permeate; and Faraday, Liebig, and other chemists established the principles of a thorough analysis. During the past 50 years many mineral springs have been discovered, and all of note have repeatedly been analyzed. ”

“ On the other hand, fresh supplies are derived by the atmosphere and by running water, as before stated, from the disintegration of rocks and their organic contents, and through the agency of mineral springs from the interior of the earth, from whence all the elements before mentioned, which enter principally into the composition of animals and vegetables, are continually evolved. Even nitrogen is found, by chemists, to be contained very generally in the waters of mineral springs. ”

“ The central cores of many of the now deeply eroded ranges consist of granite and other similar rocks, and are surrounded by sedimentary beds which range in age from the oldest stratified rocks now known to the youngest. Igneous rocks in great variety and in all forms incident to an extruded or volcanic and intruded or plutonic origin are present. The many disturbances that have occurred have led to the formation of mineral veins and the impregnation of rock masses with ores of various kinds—such as gold, silver, lead, copper, etc.—which have been mined with great success at many localities. ”

“ The development of soils by weathering should not be regarded as a special process of rock alteration, unrelated to processes producing other mineral products. Exactly the same processes that produce soils may yield important deposits of iron ore, bauxite, and clay, and they cause also secondary enrichment of many metallic mineral deposits. ”

“ Later, as the cooling-process continued, there would be shrinkages of the earth's crust causing other fissures; intrusive granites further dislocated and upheaved the slates. About this age, probably, when really dry land began to appear, came the first formation of mineral lodes, and the waters, heavily charged with silicates, carbonates of lime, sulphides, etc., in solution, commenced to deposit their contents in solid form when the heat and pressure were removed. ”

“ Evidently the development of sediments from igneous rocks has involved the destruction of much of the feldspars and ferro-magnesian silicates, and the building from the elements of these destroyed minerals of more quartz, white mica, clay, dolomite, calcite, chlorite and limonite. The composition of the minerals of the sedimentary rocks is such as to indicate that the constituents of the air and water have been added in important amounts to accomplish this change of mineral character. ”

“ This does not apply to the organic deposits, for each type of which there is a peculiar mode of formation. To illustrate the typical formation of sedimentary rocks, we may look at the fate of a granite when exposed. At once the surface is attacked by changes of temperature, frost and rain. The various minerals of the granite expand and contract with every change of temperature, but each component mineral has a different coefficient of expansion under heat, so that minute cracks are quickly formed between the minerals. ”

“ The ore lies in this marly clay, and [Pg 163] is often accompanied by sulphate of barytes and calcareous spar. The country is particularly characterized by radiated quartz, which is strewn in detached pieces over the ground, and is also found imbedded in the soil at all depths. This substance is here called blossom of lead, or mineral blossom. Pyrites, and some other ores of iron, are also found in detached masses upon the surface, and, very rarely, lead-ore. ”

“ But at a later period, when a considerable thickness of sandstone and marl had accumulated, eruptions broke out, and lava and tuff were deposited, at some spots, alternately with the lacustrine strata. It is not improbable that cold and thermal springs, holding different mineral ingredients in solution, became more numerous during the successive convulsions attending this development of volcanic agency, and thus deposits of carbonate and sulphate of lime, silex, and other minerals were produced. Hence these minerals predominate in the uppermost strata. ”

“ Mechanical erosion of preëxisting mineral deposits or rocks and their transportation, sorting, and deposition are responsible for the placers of gold, tin, tungsten, platinum, and various precious stones, and for certain iron sands and conglomerates. Sands, sandstones, shales, and certain clays and bauxites also belong in this group. These deposits may be formed under air or under water, and under various climatic and topographic conditions. During the process of formation the minerals of differing density are more or less sorted out and tend to become segregated in layers. ”

“ But even when the beds are conformable, they can usually be separated into groups, depending upon differences of mineral character, or changes which have occurred in the mode of deposition. One group of beds, for example, may be largely composed of limestone, another of sandstone or shale. One group may be distinguished by containing some special mineral, as, for example, rock salt or coal, while others may be destitute of such special minerals. ”

“ But other rocks contain grains of quartz, a hard mineral which cannot be decomposed, and it always forms sand. Certain classes of rocks, too, such as the limestones and some iron-ores, are completely dissolved by water holding carbon dioxide in solution, and nothing is left to form soil, except usually a small proportion of insoluble impurities like sand or clay. ”

“ Under the influence of percolating, heated waters, new minerals are formed in sedimentary or igneous rocks, and rocks once metamorphosed may undergo additional changes. Mineral matter previously widely disseminated through rocks is, under the action of percolating, heated water, brought together and the regeneration and crystallization of a large variety of ores and minerals result. The birthplace of a large variety of ores and minerals is in the zone of metamorphism. It is in metamorphic rocks that the geologist looks for gems, the precious metals, crystalline marble, magnetic iron, etc. ”

“ This well-marked hill, situated at the extreme northerly end of the depression, consists of a mass of ferruginous material, including limonite, pisolitic iron-ore, red and yellow ochre, etc., lying on a series of sandy shales, clays and sandstones belonging to the Cenomanian (Series No. 7) . Thin bands of limonite, etc., occur in the clays and sandstones, but the great mass of mineral appears to form a distinct deposit capping, and in part replacing, the former. The iron-ore occurs in every stage of purity. ”

“ If the quantity of siliceous and aluminous ingredients brought up by such springs were great, instead of being utterly insignificant, it might be contended that the mineral matter thus expelled implies simply the decomposition of ordinary subterranean rocks; but the prodigious excess of carbonate of lime over every other element must, in the course of time, cause the crust of the earth below to be almost entirely deprived of its calcareous constituents, while we know that the same action imparts to newer deposits, ever forming in seas and lakes, an excess of carbonate of lime. ”

“ We observed a single mass of the rock, an imperfectly columniform structure, apparently organic. The rock is rather vesicular than cavernous in its structure. The heavy deposit of diluvium conceals the surface. But if the appearances in the mine-diggings are to be received as general indicia, the surface of the concealed rock is extremely rough and irregular, standing up, in the mineral soil, in huge lumps, which renders the general depth at which it may be reached, a question of great uncertainty. ”

“ A great mineral country is usually marked by the outcrops of the veins being persistent in their courses and traceable for many miles, though very probably many breaks may occur in these outcrops. The rocks associated with great ore bodies are lime, porphyry, granite, shales, slates, quartzites, and diabase. Fragments of mineral and gangue, known to the miners as float, may be littered over the hills and encumber the courses of the stream. ”

“ The magmatic waters, on the other hand, seem to be of paramount importance and of great efficiency in producing the deposits of ores in the contact zones next eruptives, and in the formation of veins which are reasonably to be attributed to uprising heated waters in regions of expiring vulcanism. They start with their burden of dissolved metals and minerals under great heat and pressure, amid conditions favouring solution, and migrate to the upper world into cooling and greatly contrasted conditions which favour precipitation. ”

“ By the erosion of the igneous rocks the metals have been distributed among sedimentary strata, and even the sea has taken into solution an appreciable amount of gold and other metals, but in this widely diffused condition they are wholly useless to man. The concentration which has made them available is due to the interaction of many agencies. Earth movements fracturing deeply the rocks of the crust, the intrusion of heated masses, the circulation of underground waters, have all cooperated in the concentration of the metals of mineral veins. ”

“ They are not deposited in the Jurassic formation, as are those in France, Switzerland, and Germany, but in a dolomitic limestone of the lower Carboniferous series. The mineral is rich in bitumen, of less fusible quality than the bitumens of France and Switzerland, and has not been produced in the compressed form. It is extensively made into mastic, the fabrication of which already amounts to ten thousand tons a year, and is rapidly increasing.—La Nature. ”

“ There the amount of evaporation is often sufficient to cause a re-deposit of the mineral in solution. If it be lime, a white crust gathers along the sides of the stream, delicately enveloping grass-stalks, leaves, twigs, snail-shells, and other objects, which it may meet with in its progress. Such "petrifying" springs, as they are popularly termed, occur abundantly in our limestone districts. It should be borne in mind, however, that they only produce an incrustation round the organic nucleus, and do not petrify it. ”

“ But the springs called mineral contain an unusual abundance of earthy matter in solution, and the substances with which they are impregnated correspond remarkably with those evolved in a gaseous form by volcanoes. Many of these springs are thermal, i. e., their temperature is above the mean temperature of the place, and they rise up through all kinds of rock; as, for example, through granite, gneiss, limestone, or lava, but are most frequent in volcanic regions, or where violent earthquakes have occurred at eras comparatively modern. ”

“ Soils of this kind, which are usually rich, are common in many limestone valleys of the Appalachian Mountains. In the case of shale rock, which is hardened mud, the cementing materials are removed, some chemical changes in the minerals may take place, and the rock crumbles to a claylike soil. What happens to a very hard, resistant igneous rock like granite when attacked by the weather? Such a rock always consists mainly of the two very common minerals feldspar and quartz, usually with smaller amounts of other minerals such as mica, hornblende, augite, or magnetite. ”

“ These conditions promote chemical change: much silica (the mineral quartz) , lesser amounts of carbonate of lime (the mineral calcite) , and iron oxide are precipitated about the loose sand grains, firmly cementing them together into a solid rock. A cycle has thus been completed; the dense rocks composing a continent have passed by the process of weathering into incoherent sand and clay, which, when transported to the ocean floor, become again converted into solid rock. ”