428 A. A. JULIRN — AMPHIBOLE SCHISTS OF MANHATTAN ISLAND 



Fine-grained dioritic gneiss and hornblende gneiss, passing into biotitic 

 gneiss. 



Massive amphibolite, actinolite and tremolite rock and schist, ophi- 

 ealcite and serpentine. 



P YR OXE NIC R CKS 



I have not found a published description of pyroxenic rocks on this 

 island by any observer. The earliest statement seems to have been that 

 of Mather* that " augite rocks have been found at a few localities," who 

 further mentions, under the head of " greenstone "in Putnam and West- 

 chester counties : 



"In some places it has the aspect of compact trap, like basalt, but more fre- 

 quently the hornblende predominates and gives its character to the rock. . . . 

 Many of the masses classed with this rock would be classed with sienite but for 

 the fineness of the grain, being of about the texture of a sandstone, composed of 

 black hornblende, with grains of white and gray feldspar." 



I am indebted to Dr J. J. Friedrich of this city, who has made col- 

 lections of our local rocks, for the following notes concerning localities : 

 At East Ninety-fifth and Ninety-sixth streets, between Third and Lex- 

 ington avenues, pyroxenic rocks in great abundance, in an extensive 

 excavation, associated with chlorite schist containing pyrrhotite and 

 pyrite. Other localities occurred from Ninety-fifth to One hundred and 

 second street, between Third aud Fifth avenues, and less commonly 

 east of Third avenue, with distinct evidences of the process of serpentin- 

 ization. 



Dr Anthony Woodward, of the American Museum of Natural History 

 in New York city, an active collector of our rocks, has informed me of 

 a similar locality at West One hundred and tenth street, west of Ninth 

 avenue. There is also the latest statement t of Mr F. J. H. Merrill of 

 the general view : 



^'' Basic dikes. — Intercalated with and injected into the Hudson schist and also 

 the Fordham gneiss, we find at a great number of localities on Manhattan island 

 and in Westchester county hornblendic and augitiCj bands and lenses of limited 

 thickness, usually only a few feet. In composition and structure these rocks re- 

 semble diorites and diabases, and their general characters suggest that they were 

 originally eruptive rocks, though at present they are in a foliated condition." 



No pyroxenic rocks, however, were found by Dana or by myself at 

 any localities on the island, nor is there a single specimen of these in the 

 public collections in this city, though many of dioritic and hornblendic 

 gneiss and schist from the above-stated localities ; nor iu over fifty thin- 



* Nat. Hist. N. Y., part IV (1843), pp. 531-532. 



t U. S. Geol. Survey, Geol. Atlas, New York city folio, no. 83, 1902, p. 3 ; also N. Y, State Mus. 

 Rep. L, 1896, pp. 23, 28, 31, etcetera. 



