Dolomite occurs to a limited extent as such; most of it, being in the form of gurhofite crystals, may be occasionally found with aragonite of a light pearly gray color and rhombohedral crystals. As before noticed, Staten Island is the best locality for this species.
In places the limestone is perfectly crystallized, and of a pure white or other color, when it forms an attractive mineral, and often worth removing. The limestone of the main quarry, carefully averaged, was found to have the following chemical composition.
Lime. 11.09 Magnesia. 37.94 Carbonic acid. 30.61 Silica. 10.22 Water and loss. 4.90 Iron and alumina. 5.24 ------ 100.00
In places it is spotted with the serpentine, and judging from its rough state resembles "verde antique," and at that of a beautiful color; samples of this should be obtained.
This mineral occurs very plentfully in the space between the limestones and gneiss. It is generally of a flesh red color and often in very perfect crystals, in some instances an inch and a half in length; as its hardness is 6, it can be readily distinguished from calcite, which it much resembles, but which has only a hardness of 3, and dissolves with effervescence in acids.
A visit to this locality is a delightful manner in which to spend a holiday or other time of leisure; and as it affords so many interesting and valuable minerals, it forms a very profitable trip as well. In reaching it many interesting localities are passed, and if one has an early start these may all be visited. I will describe a few of these, which are alike possessors of beautiful scenery and instructing geological features and not far from the main line of travel.
Starting from the Erie depot, on the Greenwood Lake road, the first stop may be at Arlington, about seven miles west of Jersey City. Here a visit to the Schuyler copper mine may be profitably taken; and as I have written a full account of this locality in a previous portion of these articles, I will not reiterate it here, but refer to that paper. The mine, I might add, is only a mile north of the railroad station, and on Schuyler Avenue, a short distance north from its junction with the Jersey City and Paterson turnpike. Coming back to Arlington depot, and walking on the track for about a quarter of a mile west through the deep cut, the manner in which the sandstones and shales which constitute so large a portion of New Jersey are laid and arranged can be seen to great advantage, this being one of the finest exposures in the formation. At a point about equidistant from either end is a fault in the layers of shales and sandstone; this fault is noticeable as a slight irregularity in the otherwise continuous sides of the cut, and is a point at which the layers of rock on the east have fallen vertically, the western side remaining in its original position.
This fault has a thrust of only three feet, but is an instructive example of faults which occur on a tremendous scale in some of the other formations. It will be noticed that between the two edges of the separated layers there is a deposit of a talcky substance, which has been derived from infiltrating waters. Fissure veins are generally in positions of this kind, formed and filled in a similar manner, but with the various metallic ores. Passing further west a short distance we reach the Passaic River, and walk along its banks for a mile north to the Belleville bridge; at this point is the intake of the Jersey City water works, with their huge Worthington pumps and other accessories, which may be conveniently visited. The Passaic River is then crossed, and the train on the Newark and Paterson road may be taken for three miles to Avondale, from whence it is two miles east to the Belleville sandstone quarries, or the bank of the Passaic may be followed and the quarries reached in an hour from Belleville. Here again are met the sandstones and shales, besides another and larger fault, and many interesting features of the sandstone and its quarrying may be examined. The railroad station having been regained, Paterson is the next point of interest.
The first thing noticeable in approaching the city are the quarries in the side of the hills to the south, and these may be visited the first; they are but a short distance southeast of the station. Here the sandstone will be found in contact with the trap above and the layers of basalt, trap, tufa, sandstone, shales and conglomerates are exposed. Regaining the nearest railroad track (the Boonton branch of the D., L. & W.R.R.), this is followed for some distance west, when the various strata can be examined in the cut of the railroad and a fault of nearly sixty feet in the trap; this is noticed as a depression in the face of the cliff, and it may be seen by the superposition of the layers of trap and basalt. Where the fault occurs a short distance further west, there is another smaller fault. A visit to the Great Falls of the Passaic is a very pleasurable diversion at this point, and these are about a half mile north of this locality. Here the arrangement of the trap and sandstones can be again profitably studied, and the mineralogical localities which I have described in a former one of these articles examined, not omitting the one at West Paterson, wherein so much phrenite may be found.
Taking the train from West Paterson to Little Falls, a walk of a few miles south brings us to the Little Falls, and here is another interesting locality wherein the contact of the sandstone and trap may be examined and the numerous additional phenomena studied. A quarry near the Falls is the best point in which to find these exposures, and from the viaduct crossing the river an excellent view of the surrounding country may be obtained. Regaining the train, Montville is soon reached and visited, and after this, if time sufficient Boonville, two miles west, may be taken in, or it may be necessary to go there to catch a return train, as but few stop at Montville. At Boonton there are many interesting features--iron works furnaces, localities in which fossil remains are found, footprints, conglomeritic beds, and many other things, of which I will endeavor to give a detailed account in some other of this series of articles.
[Footnote 1: See SCIENTIFIC AMERICAN SUPPLEMENT, No. 363.]
[Footnote 2: See SCIENTIFIC AMERICAN SUPPLEMENT, No. 363.]