_Pyrites_.--White and yellow iron pyrites are abundant in the gneissic rock adjoining the limestone, and frequently very fine, perfect crystals may be found handsomely dressed upon the rock. There is no particular portion of the quarries in which they abound. _Biotite_.--This is a variety of mica in small crystals, of a dark brown color, and quite plentiful in the gneiss inclosing the veins of limestone. Up in the older quarries it is more abundant; on the north wall of the vein it is often in very fine specimens, and there even in large number, in a locality, generally a pocket in the gneiss. _Tremolite_ is quite abundant on a large mass of limestone in the extreme upper quarry, which is a short distance east of the main one, over a small hill. The tremolite occurs in white crystals, about a quarter inch in width and from a half to three inches in length. The crystals are opaque, but very smooth and glistening, lining cavities in this mass of limestone. It is a variety of hornblende, composed of silica, lime, and magnesia, with a little alumina. It probably occurs in places in the vicinity of this block, and in finer specimens, as these are frequently, when near the surface, much weathered and worn. This is a characteristic granular limestone mineral, and a very interesting one. We will again meet it when examining the New York city localities. _Aragonite_ occurs in very small masses, of a light yellow color and fibrous structure, between layers of serpentine. When they are separated by a small interspace, as it frequently is, the fibers are very large, coarse, and brittle, and thus do not resemble asbestos, although in some instances they might be mistaken for picolite, but, distinguished from it by effervescing on contact with a drop of acid, as it is a carbonate of lime, and also containing a trace of iron. I have never seen any fine specimens of it from this locality, but deeper down in the rock it may occur in greater profusion. 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. _Calcite_.--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.