422 



JULIEN 



observed alteration-products, bastite and hydrated amphibole, 

 aside from the remnants of unaltered diallage, actinolite and 

 tremolite. The analysis of the rock with the stated corrections, 

 and its approximate mineral constitution so deduced, are giv^en 

 above. 



On separation from the above figures of the percentages of 

 pleonaste, chromite, dolomite and brucite, the molecular ratios 

 obtained suggest that the predominant mineral was a metasili- 

 cate, with oxygen ratio R : Si :: i : 2, as in pyroxene, and 

 that the products of hydration are equivalent to an orthosilicate, 

 with oxygen ratio R : Si :: i : i. The figures are, however, 

 inexact, probably through extensive removal of silica. A 

 similar treatment of Goodell's analysis of the Staten Island ser- 

 pentinoid has yielded the following results. The amount of 

 carbon dioxide was included by the analyst in the percentage of 

 water and stated to be small. 



Chemical Composition of Staten Island Serpentinoid. 



Mineralogical Constitution. 



1 



! 

 /-s t^ 



n 





0-^ 



fa H 



.06 



•23 

 .14 



.24 



.86 



g^ 



^ 



a ON 



D as 





.63 



3 



• 



Magnetite 



.20 



•77 

 2.79 

 1.32 



41.05 



41.06 

 7.91 

 4.38 



.52 







100.00 



.93 -52 



18.65 .19 



17.14 .35 



1 



.49 



.14 

 6.45 







.36 



.62 



5.61 

 2.45 



4.3« 





Chromite 



Chlorite 



.05 - 

 .84! - 

 .29 .40 



5.35'9.55 



17.10 — 

 5.46 — 







Dolomite 







Diallage with amphi- 

 bole and bastite 



Serpentine with villar- 

 site and talc 



— 



Brucite with bronzite.. 

 Water 



— 



Moisture 



. — 





•52 



From these results we infer that in the rock at these localities 

 serpentine plays only a secondary pai't. 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 accor- 

 dance with Von Drasche's excellent suggestion. Nevertheless, 



