78 



PROCEEDINGS S. 1. ASS X ARTS AND SCIENCES. 



[Vol. I 



teristics of serpentinoids next follows, in order to prove the author's 

 view that they must be regarded as derived from ultra-basic igfneous 

 rocks. In this discussion a table of analyses of samples from various 

 localities is given, which includes one of "Dark green serpentine," 

 from Castleton Corners, with a specific gravity of 2.55, made by G. A. 

 Goodell, as follows: 



SiO, 36.72 



ALO3 

 Cr2 O3 



FeO 

 MgO 

 CaO 



HaO 



1.06 

 0.49 

 6.59 

 1-53 



2g.og 

 9-95 



14-54 



From this analysis the author deduces the probable mineral constitu- 

 ents to be 



Serpentine, with villarsite and talc . . 41.06 



41.05 



7-91 

 2.79 



1.32 

 0.77 

 0.20 

 4.38 

 0.52 



tine plays only 



Diallage, with amphibole and bastite 



Brucite, with bronzite .... 



Chlorite ... 



Dolomite ....... 



Chromite . , . . . 



Magnetite . . , 



Water . . . , . . 



Moisture . . . . . 

 and infers "that in the rock from these localities serpei 

 a secondary part. Only confusion can result from designation of the 

 mass as a rock serpentine on the ground of resemblances in chemical 

 composition and physical characteristics. Varieties of such imperfect 

 serpentinization should be preferably discriminated as serpentinoids, in 

 accordance with Von Drasche's excellent suggestion." 



In discussing the origin of the probable igneous rock from which the 

 present serpentinoid was derived the author says: "In the Staten Is- 

 land rocks the composition is allied to that of combination of olivine 

 and bronzite with diallage. The predominance of amphibole rich in 

 lime and magnesia, with traces of pyroxene, olivine, and bron2ite, sug- 

 gests derivation directly from a basic hornblende schist, derivative in 

 its turn from an ancient diallage-, bronzite- or enstatite-rock, pass- 

 ing at one point at least into peridotite." 



The theoretical alteration of the original igneous mass into schists, 

 and the subsequent progressive alteration of the component minerals of 



