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Published online by Cambridge University Press: 17 March 2016
The inferior division of the Carboniferous series in Derbyshire and North Staffordshire, composed of calcareous rocks and shales, and forming the Mountain Limestone group of those counties, presents, particularly about the neighbourhood of Alstonfield, some very interesting and remarkable associations of metallic minerals with certain mechanical disturbances of the strata; moreover, these associations are not to be indiscriminately classed with the general phenomena of the mineral veins of the districts in question, but must be considered as special facts requiring a separate consideration and explanation. Their existence is no new discovery, since they have been recognized from the earliest times that mines have been worked in the places where they occur, and where also they are at most times regarded as valuable features, inasmuch as the richest deposits of ore have been found in connection with them; indeed, so decidedly has this been the case, that, in working the mines, much of the future success has been calculated by the amount of probability of any particular vein intersecting the disturbed beds; such unions having, in nearly all cases, been attended with most important results, both as respects the quantity, as well as the kind of ore met with. Nevertheless, I am not aware of their having ever received any particular attention from geologists, nor of their having been anywhere described, circumstances which may probably arise from the fact of these beds only being visible below the surface, and usually in deep mines; or they may have remained unnoticed, from the really small amount of scientific observation which in this country has been brought to bear on the facts connected with metalliferous deposits, compared with what has been done, and is still doing, in other branches of physical geology. The present article is drawn from memoranda made during several careful surveys of mines which are notable, in North Staffordshire, for exhibiting the phenomena of the saddles in great force.
page 367 note * The stratum of mean temperature lies in latitudes forty-eight degrees and fifty-two degrees north, at a depth of about sixty to sixty-four feet.
page 368 note * The outcoming of the bearing-beds is recognized, among other appearances, by the more crystalline character of the limestone, but with the exception of the occasional presence of the peroxide of iron, there is nothing to indicate the metalliferous condition which obtains in them elsewhere; and, it may be, though I have no positive knowledge of the fact, that their unfossiliferous state, as remarked in the text, is also only partitive. It is not difficult to imagine that the intense squeezing, necessary to produce the often fentastic contortions of the ore-bearing parts of these beds, would be sufficient to crush and obliterate any remains of organisms previously preserved, particularly if aided by any subsequent arrangement in the molecular agglomeration of the rock, of which there is abundant evidence in, at least, the productive portions of these strata.
page 369 note * Where galena is the associated ore, copper seldom occurs in any other form than as copper pyrites, a fact worthy of remark in connection with the paragenesis of metallio minerals.
