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SOUTH STAFFORDSHIRE.
CHAPTER V.
Description of the Rocks—continued.
4. The Coal-Measures.
General Description.
The Coal-measures of North Staffordshire consist very largely of argillaceous (or clayey) materials, more or less mingled or alternated with arenaceous (or sandy) and carbonaceous (or coaly) substances. These different beds have various local names, of which the following is a nearly complete list:—
Argillaceous Materials.—Clunch,—a tough clay, breaking into blocks; sometimes rather sandy, generally grey or yellowish.
Binds,—shaly clay, close, smooth, compact, and splitting into regular lamine, generally blue, or some shade of grey. Clod, ground, earth,—earthy clay, generally of a blue or black colour.
Batt or bass,—highly carbonaceous[1] shale, commonly very compact, and splitting into the finest laminæ, almost invariably black, and often interstratified in layers with the coal.
Fire-clay,—clay having a certain definite i He of silica and alumina in its composition with but little admixture of metallic or earthy fluxes, so that on the application of heat it forms a nearly pure silicate of alumina, and therefore makes good fire-bricks. It is generally unctuous to the touch as soon as it is got, which "the other argillaceous beds rarely are. It is commonly a brownish grey, sometimes nearly black, but sometimes quite pale.
Arenaceous Materials. —The siliceous or arenaceous beds of the coal-measures have the following local names:—
Rock.[2]—All sandstones having any degree of hardness or toughness go under this name with the colliers.
Pebbley or bibbley rock,—sandstone with pebbles, conglomerate.
Rotch, or roach, is applied to sandstone when it is softer or more brittle than rock, so as to break easily into small fragments.
Peldon,—a very hard, smooth, compact, flinty stone, with conchoidal fracture.
- ↑ It has been usual hitherto to call this "bituminous" shale, an incorrect term, inasmuch as, though it contains the components of bitumen, it does not contain that substance itself; one might almost as well in speaking of a sack of malt call it a barrel of ale.
- ↑ Under the term "rock" the miners likewise include all kinds of trap which occur in the district, using generally the distinctive terms "green rock" and "white rock," according to the colour. The only practical ambiguity that arises from this confusion of terms is in the case of the "white rock;" as, when that term is used, it is sometimes doubtful whether white sandstone or white trap is meant.
