452 A. A. JIILTEN AMPHIBOLE SCHISTS OF MANHATTAN ISLAND 



Coccolite limestone. 



Garnet pyroxene limestone. 



Enstatite limestone. 



Scapolite limestone. 



Wollastonite limestone. 



Olivine (boltonitej limestone. 



Chondrodite limestone. 



Biotite or phlogopite limestone. 

 Stage 2. Tremolite rock and schist. 



Actinolite rock and schist. 



Araphibolite, hornblenditeand hornblende schist, and gedrite rock. 



Sahlite, garnet, graphite, magnetite, epidote, or rutile amphibolite. 



Diopside rock, pyroxenite, and pyroxene schist. 



Enstatite rock and schist. 



Wernerite (scapolite) rock. 



Wollastonite rock. 

 Stage 3. (By decomposition :) , ' 



Calcite serpentine (ophi-calcite, serpentine marble or ophiolite, in part). 



Dolomite serpentine (ophi-dolomite, ophiolite, in part). 



Tremolite, actinolite, amphibole, or hornblende serpentine. 



Diopside (or pyroxene or sahlite) serpentine. 



Enstatite, bronzite, antigorite, or bastite serpentine. 



Olivine (boltonite) serpentine. 



Mica serpentine. 



Tremolite, actinolite, or amphibole steatite. 



Talc and chlorite schists. 



As to stage 1, the incipient changes have been recognized throughout 

 the dolomitic limestones of Manhattan island and Westchester county by 

 permeation, in little nests, of tremolite, diopside, coccolite, phlogopite, 

 and sometimes actinolite, scapolite, and biotite ; but no traces of au^ite. 

 hornblende, garnet, enstatite, wollastonite, olivine, or chondrodite have 

 been anywhere observed in our limestones. 



A few members of stage 2, according to Dana,* were represented b}^ 

 the amphibolite, actinolite, and tremolite schists at West Fifty-ninth 

 street and Eleventh avenue and the pyroxene and hornblende rocks at 

 New Rochelle; but in Massachusetts amphibolites derived from lime- 

 stone are characterized by large intermixture with albite and oligoclase, 

 with tendency to a peculiar pseudoporphyritic texture,t both features ab- 

 sent from the amphibolites of this region. Though alteration of lime- 

 stone into diopside rock does not occur on Manhattan island, this is well 

 shown in the lime quarries of a neighboring region, at Montville and 

 Mendham, New Jersey ; nor has pyroxenite, enstatite, scapolite, or wol- 

 lastonite rock ever been found on the island. 



* Am. Jour. Sci., vol. xx, 1880, p. .i'2. 

 t Emerson : Op. cit., p. 304, etc. , 



