The Sing Sing marble, however, although an admirable building stone for many purposes, is of comparatively coarse and inferior quality, becoming stained in the course of time by the action of the sea air on account of the presence of grains of iron pyrites. Marble is also quarried at Tuckahoe. Abundant indications are afforded of extensive and radical glacial action. " Croton Poiut, on the Hudson, and other places in the county, show evidences of glacial moraines. Deep stria? and lighter scratches still remain upon many exposed rock surfaces, and others have been smoothly polished." A prominent feature is the presence in greal profusion of large granite bowlders, undoubtedly transported by glaciers from Massachusetts and New Hampshire, with an interrm*
EARLY
NAVIGATION
HIGHLANDS
mingling of bowlders of conglomerate from the western side of the Hudson, the latter containing numerous shell fossils. The so-called " Cobbling Stone," in the Town of North Salem, is a well-known specimen of the glacial bowlders of Westchester. It is a prodigious rock of red granite, said to be the solitary one of its kind in the county. The minerals found in the county, in greater or lesser quantities, embrace magnetic iron ore, iron and copper pyrites, green malachite, sulphuret of zinc, galena and other lead ores, native silver", serpentine, garnet, beryl, apatite, tremolite, white pyroxene, chlorite, black tourmaline, Sillimanite, monazite, Brucite, epidote, and sphene. But Westchester has never been in any sense a seat of the mining industry proper, as distinguished from the quarrying. In early times a silver