Another peculiar variety of sandstone occurs, in connection with the sulphuret of lead, at the old mines of St. Michael, and at many places thereabouts. This bears apparently the same relation to the common sandstones, as the crystalline limestone above {306} mentioned does to the earthy varieties, and it alternates with and passes into the common rock in a similar manner. Its particles are crystalline, and appear to remain undisturbed in the position in which they were originally deposited from solution in water. Nevertheless the aggregate is manifestly secondary, and embraces the relics of many organized beings, as is common in the other secondary rocks.
There is also about the lead mines a sandstone composed of small glimmering grains of transparent quartz, and so loosely cemented as to fall rapidly to pieces, forming a light gray sand. In this variety we have sometimes observed the lead ore either disseminated, or forming horizontal veins between the laminæ of sandstone. An examination of some spots might lead to the conclusion that the soil in which most of the lead has hitherto been found, has resulted from the disintegration of a sandstone of this kind.
Sandstone, though often covered at the surface by compact limestone or some other stratum is probably the rock which occurs in the greatest quantity throughout every part of this range of mountains. It is the prevailing stratum in all the country between the Arkansa and Red rivers, from the confluence of the Mamelle westward; rising to the height of two or three thousand feet, to form the summits of the Cavaniol, Sugar Loaf, and Mt. Cerne, and to a less considerable elevation at the Mamelle, Magasin, Caslete, and Short mountains.
North of the Arkansa it forms the body of the Chattahoocke mountain, and of many nameless elevations, which diversify the surface from the sources of the Little Red river to the Mississippi. Beds of coarse conglomerate or puddingstone, are met with in many places; but these are particularly frequent in connection with the inclined or transition sandstones about the Washita.
Native Argil.—Nine miles west of Bainbridge, on {307} the road to Jackson, and on the right bank of the Mississippi, near the head of Tiawapeti bottom, also in various other places in this vicinity, there are extensive beds of perfectly white native argil, of about the hardness of common chalk, for which it has often been mistaken.[85] See Schoolcraft's "Catalogue of Western Minerals," art. 1st. Notwithstanding Mr. Schoolcraft's confident assertion, it must yet be considered doubtful whether any chalk has ever been found in the region under consideration.
Specimens of the substance called chalk by the inhabitants, were collected at several places between Cape Girardeau and St. Louis. Also on the north side of the Missouri, on the road from St. Louis to Franklin. Some of these which were brought to New York, have been examined by my brother, Dr. J. James, and others, and were found to consist principally of argil, none of them occasioning the slightest effervescence with acids.
This substance, whatever it is to be considered, is distributed extensively throughout the country lying around the confluence of the Missouri and Mississippi. Some specimens have been sent from Illinois to the Lyceum of Natural History at Troy, where they are spoken of as a "littrographic carbonate of lime;" but whether any experiments have been made to ascertain their real character we have not been able to learn. We have not, from our own observation, found occasion to confirm the statement, that nodules of flint are found imbedded in this substance; but we have commonly found it accompanied by the flint rock already mentioned, which has in many respects a manifest resemblance to the flints occurring in chalk formation. We have sought in vain for the remains of echini and other animals so common in chalk beds.
Argillite.—Of the older secondary rocks, we have observed in the Ozark mountains only the inclined {308} sandstones and conglomerates above mentioned, and a limited formation of argillite, extending a few miles around the hot springs of Washita, and re-appearing on the Arkansa at and above the town of Little Rock, being usually accompanied by vast beds of petrosilex. This latter ought, perhaps, to be considered a distinct stratum, but south of the Arkansa we have not been able to trace it uninterrupted for any great distance.
Mr. Nuttall, in his valuable Journal of Travels into the Arkansa Territory, mentions grauwacke slate as occurring along the Arkansa river near Little Rock, p. 105. We have observed none here in any considerable degree similar to the grauwacke slate of the transition mountains of New York, or even to that of the Alleghanies. We are aware, however, that some of the aggregates which we call sandstones, have all the characters attributed to grauwacke slates, "grauwacke is a complete sandstone,"[86] and in a district where both are so intimately blended as in that we are considering, perhaps it is unnecessary to attempt any distinction between them; or we may persevere in the use of the two names at the same time, acknowledging they are both applied to the same stratum.