By NELSON H. DARTON.
Montville, Morris County, New Jersey.—This locality is an old one, and well known to mineralogists. It is outside of the limits prescribed in introducing this series of paper, but by only a few miles, and being such an interesting locality, I have included it in the granular limestone, which occurs in a small isolated ridge in the gneiss within a space of ten acres, about two miles north of the railroad station of Montville, on the Boonton Branch of the Delaware, Lackawanna, and Western Railroad, and is reached by a road running north from about a mile east of the railroad station. This road branches into two at the limestone kilns, about a mile from the railroad track, and the left hand branch is taken, which leads more directly to the quarry, which is on the right hand, about a mile further on, and quite conspicuous by the loose rock lying in front of the quarry. It is on the property of a Mr. John J. Gordon, and produces a very fine limestone for use in the furnaces and forges in the vicinity, as well as lime for agricultural purposes, it being the only limestone in the vicinity for fifteen miles. Between it and its walk of gneiss occur veins of the minerals so characteristic of the locality, and for which it has become famous—serpentine, asbestos, phlozopite, gurhofite pyrites, biotite, aragonite, dolomite, tremolite, and possibly others in lesser quantity.
Serpentine.—All the varieties of this species, and of every color from nearly white to black, is profusely distributed through the limestone in the lower or main quarry in veins and pockets. It is generally soft, translucent, and to be found in masses from a pea to a cubic foot in size. Much of it is of a pure oil green color, rich and translucent, making a very fine and attractive looking mineral specimen. No difficulty need be experienced in producing all the varieties of this mineral, as much has been removed and may be found in the vicinity of the quarry, as it is always carefully separated from the limestone as being useless, and thrown aside, or in some instances, when of peculiar beauty, sold as specimens. The variety of serpentine known as marmolite, which is made up of numberless plates of the mineral packed together similar to mica, but of the green color of the serpentine picolite, or fibrous serpentine, also frequently occurs of a light grass green color, and is a very interesting variety.