Limestone

“ The same causes that produced the layers of peat or sand, or limestone, or clay, which we find by examination of the earth's surface, are acting to-day. Coal is forming now; and so is limestone; and so is sandstone; so even is granite. But these layers or strata form very slowly, so that since man has kept historical records the thickness of new strata laid down could be measured in inches. ”

“ There is a rapid below this fall. I judged the water must sink its level, in this vicinity, about fifteen feet. On examining the character of the limestone, I discovered crystals of calcareous spar occupying small cavities. At other localities, at lower points, there were found crystals of black sulphuret of zinc, and yellow sulphuret of iron. The rock appears to be of the same age as the lead-bearing limestone of the West; it is also overlaid by the red marly clay, and I should judge it to contain deposits of sulphuret of lead. ”

“ Now, in later formations, limestone is usually an organic rock, accumulated by the slow gathering from the sea-water, or its plants, of calcareous matter, by corals, foraminifera, or shell-fish, and the deposition of their skeletons, either entire or in fragments, in the sea-bottom. The most friable chalk and the most crystalline limestones have alike been formed in this way. We know of no reason why it should be different in the Laurentian period. ”

“ Limestone.—Something concerning the origin of limestone has already been given in the preceding paragraphs, but because of the importance of this formation, it may be added by way of summary that shallow seas free, or nearly free, from terrigenous sediment, and abounding in lime-secreting life, furnish the conditions for nearly pure deposits of limestone, and that most of the limestone within the areas of the present continents appears to have originated under such conditions. The common notion that limestone is normally a deep-water formation is a serious error. ”

“ When, therefore, we find great and conformable beds of limestone, such as those described by Sir William Logan in the Laurentian of Canada, we naturally imagine a quiet sea-bottom, in which multitudes of animals of humble organization were accumulating limestone in their hard parts, and depositing this in gradually increasing thickness from age to age. ”

“ Most frequently the limestone, which has been subjected to the destructive power of the elements, is worn into pinnacles of curious spiral shapes. Where the river washes the base of these formations, a high and precipitous wall of rock casts its shadow over the water. ”

“ It may therefore be considered as a discovery of some importance, that we possess, in this country, a species of limestone which, when used for purposes of extracting lime, and in the preparation of mortar, is capable of communicating to the cement all the properties of the pulvis Puteolanus. ”

“ The extent of the limestone which I have now been describing is considerable. The mass is of great thickness, and from the obliquity of its section a very large horizontal surface is exposed. As the beds run towards the north they may be traced to a considerable distance up the hill on the right of the river, but dipping to the south they plunge into the opposite hill and disappear. Independently of the steatitical matter which is mixed with this rock, some interesting minerals are found imbedded in it. ”

“ When the sandstones prevail, large tracts lie naked, or bear a thin and stunted heath; where the shales abound, the naturally difficult soils of the coal shales again recur. These rocks are generally found on the outskirts of our coal-fields.
13. The Mountain Limestone, 800 to 1000 feet thick, is a hard blue limestone rock, separated here and there into distinct beds by layers of sandstones, of sandy slates, or of blue shales like those of the coal measures. The soil upon the limestone is generally thin, but produces a naturally sweet herbage. ”

“ The former is considered by [Pg 185] the diggers as a flinty stone; the latter is called rotten limestone; and, from its crumbling between the fingers, and falling into grains, there is a variety of it called sandstone. It is all, however, a calcareous carbonate, will burn into quicklime, and, as I find on experiment, is completely soluble in nitric acid. As no remains or impressions of shells, animalculæ, or other traces of animal life, are to be found in it, I conclude it to be what geologists term metalliferous limestone; a conclusion which is strengthened by its semi-crystalline fracture. ”

“ The variety of limestone called OOLITE is composed of numerous small egg-like grains, resembling the roe of a fish, each of which has usually a small fragment of sand as a nucleus, around which concentric layers of calcareous matter have accumulated. ”

“ The lakes disappeared, and above their deposits, as above the rest of England and nearly all Europe except Scandinavia and patches of Spain, Italy, and the Balkans, a deep ocean rolled, and for many thousands of years deposited a grey ooze of limestone. This limestone is called the Carboniferous or Mountain Limestone. But as time went on this old sea floor began to be slowly raised, and in the shallower waters a great quantity of coarse sand and stones and conglomerate—the Millstone Grit, as it is called—was deposited. ”

“ Compact limestone, which is earthy or crystalline, brown, grey, mottled or ribboned, and slaty in the bottom beds. The crystalline is chiefly carbonate of lime, but the earthy sometimes contains as much as 44.9 per cent, of carbonate of magnesia. It has a thickness of from 150 feet to 200 feet, but contains few fossils, only eighteen species having been found in it: it appears, however, to have been throughout a pelagic deposit.
3. Fossiliferous limestone, which has a thickness of about 150 feet, is generally light yellow, compact or crystalline, with little appearance of stratification. ”

“ The limestone is found in layers, in blocks, and masses, disseminated among the clay-slate that covers the greatest part of the townships in this vicinity. When first taken from the earth, and exposed to the air, it is covered with an incrustation of a dark reddish-brown colour, that crumbles easily between the fingers, and is generally from one inch to a foot in thickness. ”

“ In mountainous districts limestones are often recognizable by these peculiarities. The chalk downs are celebrated for the close green sward which they furnish. More impure limestones, like those of the Lias and Oolites, contain enough insoluble mineral matter to yield soils of great thickness and value, e.g. the Cornbrash. In limestone regions all waters tend to be hard, on account of the abundant carbonate of lime dissolved by percolating waters, and caves, swallow holes, sinks, pot-holes and underground rivers may occur in abundance. ”

“ Thus a group of shales followed by a fossiliferous limestone would almost always mark the lapse of a much longer period than an equal depth of sandy strata. A thick mass of limestone, made up of organic remains which lived and died upon the spot, and whose remains are crowded together generation above generation, must have demanded many years or centuries for its formation. ”

“ The limestone is so traversed by joints and lines of shrinkage, that the water rapidly sinks down into its mass, and collects in small streams, which owe their direction to the dip of the strata and the position of the fissures. ”

“ Limestone.— Large deposits of Nummulitic limestone are found in the older Tertiary formations of North- West India. It yields a pure lime and is used in large quantities for building purposes. The constant association of these limestones with shale beds, and their frequent association with coal, naturally suggest their employment for the manufacture of cement ”

“ Limestone, sandstone, and clay, which constitute so many of the stratified masses, are forms of mineral aggregations such as never occur among granites, basalts, porphyries, &c., which make up a large portion of the unstratified rocks. ”

“ To preserve uniformity in the colours which represent the different rocks I have here also tinged the limestone blue. It is white in nature. It serves to show the entire loss of the stratified character which the limestone so often undergoes in the vicinity of the granite. Specimens from this junction are also in the Society's collection. ”

“ If the quartz rock of this tract be a primitive rock, then the limestone is necessarily a primitive rock also, notwithstanding its bituminous nature, and accurately stratified structure, since it alternates with it. But, if this rock is not a primitive, but a transition rock, then the limestone also must be removed from the first class of rocks to the second. ”

“ The change proceeds outwards from fissures and bedding planes and spreads gradually through the mass of the limestone; often the transformation is complete and no unaltered rock remains. Silicification or the replacement of limestone by chalcedony, chert or quartz, is often exhibited on a large scale. ”

“ The lowest of them are the beds of the red ground, as this formation has been absurdly denominated, consisting of a coarse limestone conglomerate, above which lies a calcareous sandstone, red and white in different places, and then a deposit of red clay, containing gypsum and sulphate of strontian. ”

“ Farmers who have had experience with the use of ground limestone are as a rule satisfied with only a reasonable degree of fineness, and are able to judge the material by inspection. When limestone is ground so the entire product will pass a 10-mesh (or 2 mm.) ”

“ A soil-formation overlying limestone on the slopes of a range may be wholly derived from non-calcareous formations lying at a higher elevation, or may have been leached of its original lime-content by abundant rains. The feldspars constituting rocks designated as granite, may or may not be partially or wholly of the soda-lime instead of the potash series ”

“ Peculiar in their mineral composition, rocky structure, and the nature and distribution of their imbedded organic remains, the constituent members of the red sandstone and magnesian limestone sometimes offer many points of inquiry to the inductive geologist, and much that seizes on the imagination of those who venture freely into the unsafe regions of speculation. ”

“ The same is true of the siliceous lamina found in the limestone, as well as of the detached pieces and small points, since they are absolutely identical in composition with the smaller reticulations.
With respect to the limestone, it is subject to a variation of aspect where it approximates to the granite which it is interesting and important to notice. The colour of the great limestone mass is lead blue of various intensity, and its texture is almost universally large grained and highly crystalline. ”

“ Such a rock is typically exemplified by a coarse-grained sandstone or conglomerate, while a limestone may be naturally porous, or, like the Trenton limestone of Ohio and Indiana, rendered so by its conversion into dolomite and the consequent production of cavities due to shrinkage—a change occurring only in the purer limestones. ”

“ The mountain limestone, attaining in England to a depth of eight hundred yards, greatly exceeds in volume any of the primary limestone beds, and shews an enormous addition of power to the causes formerly suggested as having produced this substance. ”

“ But it is quite otherwise with common limestones; the mass of which, it is true, is formed of calc-spar, but owing to its origin, is in the great majority of cases so far commingled with other matters of various character, that limestones are popularly reputed to form the very best soils. “A limestone country is a rich country” is a popular axiom to which there are, on the whole, but few exceptions. ”

“ In some places we see the best of clay for bricks; whilst in other places, and those in the vicinity of the former, we find the best of sand to mould them in when manufactured. Hard limestone of the very best quality is found in detached fragments in the sides of hills, and in strata, in abundance, along the beds of streams. ”

“ The main difference between limestone and marble is that limestone is a sedimentary rock, typically composed of calcium carbonate fossils, and marble is a metamorphic rock. Limestone forms when shells, sand, and mud are deposited at the bottom of oceans and lakes and over time solidify into rock. ”

“ The fact that some distinct bands of limestone from 700 to 1500 feet thick occur here, may be connected with the escape from destruction of some few traces of organic life, even in a rock in which metamorphic action has gone so far as to produce serpentine, augite, and other minerals found largely intermixed with the carbonate of lime. ”

“ The mountain limestone alone, of the middle secondary epoch, contains more calcareous matter than is to be found in the three antecedent periods. The lias, oolites, and chalks are likewise of vast thickness. The beds of the tertiary group are less considerable; but in the gypseous marls, and numerous alternating bands throughout the clays and sands of the formation, there is the clearest evidence that the stores of nature were still abundant. ”

“ In geologic age they are of carboniferous age or older and in chemical composition they consist of limestones in which clay occurs, either uniformly disseminated throughout the rock, forming a very intimate admixture, or else interstratified with the layers of limestone, so that when the rock is broken up and burned, the resulting mixture of the constituents of the rock is very intimate. ”

“ I observed a similar structure in the red rock, but the divisions were much smaller than in the limestone strata. In both instances the appearance is very like that of amass of dried clay or starch. When the strata of limestone are not divided into those columnar concretions, they are generally separated into large irregular shaped masses by joints perpendicular to the stratification, and in many parts they are penetrated in every possible direction by contemporaneous veins of calcareous spar crossing each other like net. work. ”