Art. VI. Account of the Strata perforated by, and of the Minerals found in, the great adit to the Southampton Lead Mine.
Art. VI. Account of the Strata perforated by, and of the Minerals found in, the great adit to the Southampton Lead Mine. Communicated to the Editor by Mr. Amos Eaton, Lecturer on Geology, Botany, &c.
To Professor Silliman.
After a laborious geological excursion along M'Clure's Springfield section, for about one hundred miles, I visited Dr. D. Hunt, at Northampton. He observed that you had expressed an opinion, that an attentive examination of all the strata constituting the walls of the artificial avenue or drift at the Southampton mines, would bring facts to knowledge, which might, in some degree, subserve the cause of geological science. I am now at the mouth of the drift, having just completed the labour which you had marked out.
I employed two miners to commence with me, at the termination of the drift, which is now extended 800 feet into the hill. We broke off large specimens, at very short intervals, throughout the whole extent of the drift. We arrived at its mouth with almost a boat load of specimens. I kept a memorandum of every thing which occurred, while under ground; and I have now arranged the specimens, before the mouth of the drift, in the same order in which they were situated in the earth.
Fatigued as I am, I will make my remarks here, in the field, lest something should hereafter escape me, which is now fresh in my recollection. Beginning with the greatest distance to which the miners have penetrated, I will set down my remarks, in fact, in reversed order.
800 feet. The rock is fine-grained gray granite, traversed by veins, lined with quartz crystals, and mostly filled with calcareous spar, often beautifully crystallized. In the same veins blue and purple fluate of lime and copper pyrites frequently occur.
790 feet. The same fine-grained granite is continued, occasionally traversed by veins lined with crystals of quartz; but containing no other minerals.
774 feet. A narrow vein of sulphuret of lead, with walls lined with crystals of quartz. The fairest cubic crystals are slightly attached to the points of the quartz crystals. Yellowish crystals of carbonate of lime are often interspersed among the lead. Sulphate of barytes occurs here also; sometimes in plates meeting at various angles, and forming chambers lined with minute crystals of quartz. Minute crystals of copper pyrites and a little fluate of lime have been found here; also fine specimens of bitter spar. The walls are very compact, fine-grained granite.
760 feet. Coarse, parti-coloured granite. The felspar is flesh-coloured and white; the quartz often bluish or greenish; the mica silvery, greenish, or purplish.
725 feet. A stratum of gray-wacke slate. Texture less firm than of the same rock at the west of Pittsfield. This stratum is very distinct, and about two feet thick.
723 feet. A stratum of serpentine rock, containing very red quartz imbedded in various directions. It is very compact, and mostly green. Here it is but about three feet thick. About ten miles south of this place, on Maclure's Springfield section, near the line between Westfield and Russel, and four miles west from Westfield Academy, I found this same stratum of very great breadth. I say the same stratum, because it is situated in the granitic hill, east of the highest ridge of granite, which is evidently a continuation of this range. Perhaps I may, hereafter, give you an account of my excursion along that section of Maclure, in which I may give you a more particular description of the Westfield serpentine.
720 feet. Coarse granite, with white and flesh-coloured felspar, black and silvery mica.
700 feet. A stratum of red mica slate, about four feet thick.
694 feet. Coarse, flesh-coloured granite. This is the handsomest granite in the whole drift. Here we find the most beautiful specimens of graphic granite, both flesh-coloured and gray.
680 feet. A stratum of Kirwan's stell-stein. That is, an aggregate of fine-grained quartz and mica, without any felspar. The quartz is mostly greenish, probably coloured by the next stratum.
670 feet. Beautiful green soapstone. Very compact, but rather softer than that kind in common use for inkstands.
666 feet. A green, granular aggregate. It seems to be made up of fine fragments of quartz, soapstone, and mica, rarely a little felspar, slightly compacted together.
Remark. All the strata, from the inner termination of the drift to this place, a distance of one hundred and thirty-four feet, are nearly vertical, or a very little inclined. Here they begin to approach a horizontal position.
The green aggregate continues as far as the air-well, a distance of 66 feet, with some trifling variations in the size and proportions of the aggregated fragments.
500 feet. A granulated, schistose aggregate, chiefly of quartz and mica. Though the constituents and the form of the rock correspond very nearly with mica slate, it cannot be considered as the primitive mica slate rock. It is so slightly compacted that it can scarcely be kept from falling to pieces. Its position is nearly horizontal.
480 feet. A stratum of coal, half an inch thick. This stratum may be traced, at different intervals, one hundred and eighty feet along the drift towards its mouth. It lies between the strata of the last described schistose aggregate.
400 feet. An aggregate appears, alternating with the loose schistose rock, which resembles the red sandstone, but is of a less firm texture.
From this place all the strata, east of the soapstone, occasionally appear, for the distance of about three hundred feet. This is probably on account of their undulatory forms and horizontal position. Most of the way we find the lower part of the walls to consist of a kind of semi-indurated puddingstone. Sometimes a thin stratum of fine, loose sand occurs. At 300 feet the coal stratum disappears, passing below the bottom of the drift.
The last hundred feet is chiefly gravel, which is now supported by timbers.
Southampton, Aug. 26, 1818.