Note 97 — OBSERVATIONS ON THE MINERALOGY AND GEOLOGY OF A PART OF THE UNITED STATES WEST OF THE MISSISSIPPI. (continued 2)
Reading edition
The following are descriptions of the rocks that alternate with each other as they occur, in connection with the coal-beds at Pittsburgh; commencing with the uppermost and proceeding in a regular gradation to the lowest, that we have had an opportunity of examining.
No. 1. A loose-grained argillaceous sandstone, composed of minute grains of quartz and decomposed felspar, united by an argillaceous cement. Its colour is yellowish gray; fracture uneven; stratifications imperfect. It contains no organic remains; depth of the bed near four feet.
No. 2. Bituminous shale; natural colour brownish black, that of the streak dark gray. Before the blow-pipe it decrepitates, burns with a bright flame, emits a bituminous odour, and soon becomes nearly white. Its structure is slaty; no animal or vegetable is contained in it, small veins of clay are dispersed irregularly between the layers. Depth of the strata ten feet.
No. 3. A bed of bituminous coal; its colour is brownish black, cross fracture uneven, longitudinal slaty; fragments tabular, right angled; lustre resinous; is semihard, sectile and very brittle. Vertical and horizontal beds of indurated clay, containing a small quantity of bitumen, occur in the coal. Depth of the bed from two to eight feet.
No. 4. Bituminous shale possesses the same character as No. 2. Varies in depth.
No. 5. Indurated clay; its colour is lead-gray; fracture, in situations where it has been subjected to the combined actions of moisture and the atmosphere, irregularly slatose; in others uneven. Depth of this bed seven feet.
No. 6. Argillaceous chlorite slate, passing by regular gradations into argillaceous chlorite sandstone. Natural colour, yellowish green, that of the streak light gray; cross fracture uneven. Its powder is soft and slightly greasy to the touch; it contains no organic remains. The depth of this bed varies.
No. 7. Compact limestone, intimately mixed with alumine; it contains small veins of calcareous spar dispersed throughout the mass. Veins of angular fragments of carbonate of lime, united by a calcareous and argillaceous cement, extend irregularly through the rock. The fracture, in some specimens, is compact and earthy, in others uneven.
No. 8. Argillaceous chlorite sandstone, consisting of minute grains of quartz, chlorite slate, and talc, united by an argillaceous cement; its colour is yellowish green; fracture uneven; the powder is soft, and feels greasy to the touch; it is destitute of organic remains.
No. 9. A loose-grained argillaceous sandstone, thickly interspersed with thin laminæ of talc; its colour is light gray; fracture uneven; texture loose; it is liable to disintegration.
No. 10. Argillaceous sandstone, irregularly slatose; its colour is gray, with a tinge of yellow. Nodules of clay ironstone occur in considerable quantities through the mass of rock.
No. 11. Fine-grained argillaceous sandstone, composed of quartz and magnesia united by an argillaceous cement. Its colour is yellowish gray, which by the action of the blow-pipe passes into reddish brown. This rock contains great numbers of the impressions of the phytolites.
No. 12. Indurated clay; its colour is bluish gray, structure slatose; fracture approaching uneven; hardness inconsiderable. Impressions of small leaves occur in this, but are not numerous; they apparently consist of one species alone.
No. 13. Compact argillaceous sandstone; composed of quartz, felspar, and their laminæ of talc, united by an argillaceous cement; its colour is brownish gray. Nodules of clay ironstone occur in considerable abundance in this rock; they are formed by concentric layers, around a nucleus, which is the same in composition as the mass of their bed. Their size varies from that of a nut to an apple.
From Mr. Jessup's MS. Report.—James.