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Ch. 2: Manhattan Island

Ch. 2: Manhattan Island Page of 281 Ch. 2: Manhattan Island Text size:minus plus Restore normal size   Mail page  Print this page
78
GEOLOGY OF NEW YORK CITY
eral. Garnets of crystallographic perfection are found at­tached and inserted in the feldspar of the larger vein, as those discovered by Mr. Gilman Stanton in 1888 at 62a Street and the Boulevard, those found by Mr. Niven on Washington Heights, and the large garnet (Fig. 10) now belonging to Mr. George F. Kunz, extracted from a vein in West 35 th Street.
Tourmalines are taken out from the quartz of the granite and, as described in the section on the minerals of the island.
many other species associated with these more common and conspicuous types. The discussion of these gneisses and gran­ite, and their relative ages and the probable age of the complex or group they constitute, follows in another section.
The weathering and decay of the granite are characteristic, and can be studied at a number of localities. The feldspar softens into a white kaolin or clay, through which particles of quartz appear and undecomposed granules of feldspar. This is conspicuous at 106th Street, in the face of rock on 8th Ave-
Ch. 2: Manhattan Island Page of 281 Ch. 2: Manhattan Island
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