METAMORPHIC ROCKS. 
449 
slate described in Westchester and Putnam counties, as ranging from Blue-rock point at the 
mouth of Peekskill creek, through Gallows hill, and so on into Putnam county. It is adapted 
for use as a fire-stone for the in-walls of furnaces, but is applied to no use at present. 
At the junction of this rock with the limestone at the south end of the Tompkins upper 
quarry, the rock is loaded with carbon and pyrites. The slate is glazed with films of anthra¬ 
cite, and was supposed to be anthracite coal. Statements were made in the papers of the 
discovery of a coal mine, and the owner is stated to have been offered five thousand dollars 
for it, but refused, in consequence of its supposed value. The strike of the junction of the 
limestone and talc slate here is N. 12° E. The talcose slate and associated overlying lime¬ 
stone dip to the east-southeast, at angles of thirty to fifty degrees (Vide Plate 5, fig. 3). The 
rocks are slightly contorted. 
This limestone in Rockland county is not very extensive, but, from its location, it is of high 
economical importance. It skirts the shore of the Hudson for a mile or more, from the land¬ 
ing on the cove at the northwest point of Stony point to a little north of Tompkins’s most 
northern quarry. It extends thence to near Capt. DeCamp’s, two miles west of Grassy point, 
where it disappears beneath the Red-sandstone formation. It occupies an area of some four 
hundred to six hundred acres, and much of it lies near to the water. It also skirts the west side 
!of the marsh west of Stony point. It is not much altered by metamorphic action, but is like 
that described in the Taconic rocks. Much of it is sparry, or traversed by veins of white 
carbonate of lime. Some of it is the grey subcrystalline rock like that in Pineplains, Barne- 
gate, Newburgh, Canaan, New-Lebanon, Stephentown, Whitecreek, &c.; and some is 
dark, bluish, compact and sparry limestone. 
This stone is now quarried extensively on the banks of the Hudson at Tompkins’s quarries. 
Mr, Tompkins purchased twenty acres of this land on the shore of the Hudson in 1837, for 
one hundred dollars per acre, which was thought an extravagant price. It is a ledge of lime¬ 
stone rock seventy-five to one hundred feet above high-water mark, with deep water along 
side, so that vessels are loaded with great ease. The stratum at the new quarry is from three 
hundred to five hundred feet thick (measured across the strata), from the shore to its junction 
with the talcose slate rock. Many thousand tons of this stone are shipped annually to New- 
Jersey, where it is burnt into lime with dust anthracite at a small expense.* The lime is in 
part used as a stimulant manure in New-Jersey, and part is barrelled for the New-York mar¬ 
ket. Each acre of this limestone ought to yield, in course of working down to water level, 
six hundred thousand barrels of lime, upon which a mean profit of twenty-five cents per bar- 
vertical strata, black and more or less glazed with carbonaceous matter, so as to have given an idea to many persons that 
coal might be obtained there. Trap dykes intersect the talcose rock. Near the bridge about forty rods higher up the 
stream, or about one hundred yards across the strata, a granitic rock, having much the aspect of trappean rocks, forms 
the bank of the creek. The “marble quarry” is a little farther up the stream. 
Dr. Beck has analyzed this limestone, and has found it composed as follows : 
Silica and alumina, ... 7.25 
Carbonate of lime. 92.75 
(Fourth Annual Report on the Geology of Neui-York, p. 91.) 
Geol. 1st Dist, 
57 
