36 Johnson and Warren — Geology of Shade Island. 



Weinschenk* in veins associated with antigorite, cliopside, cal- 

 cite, amianthus and magnetite, traversing both the unaltered 

 and altered portions of a peridotite (Stubachite) which origi- 

 nally consisted essentially of olivine with some antigorite, the 

 later said to be of primary origin. Weinschenk ascribes the 

 origin of this secondary olivine to the action of deep-seated, 

 pneumato-hydro-metamorphic processes following the volcanic 

 period during which the intrusion of the peridotite took place. 

 Serpentine Veins. — At the northern end of the hill near 

 the foot of the ledge, a few narrow veins of a grayish-green, 

 fibrous, and rather brittle serpentine were observed. Small 

 magnetite grains are embedded in the serpentine. 



I. Actinolite Analysis (Warren). 



SiO 



56*00$ 



Ratio 

 •933 



•ooo 



•001 

 •100 

 •001 

 •250 

 •513 



•008 

 •044 



? 



•933 



TiO .„,. .. 



tr. 





Al . 



1-00 





Fe 



-10 



•010 



FeO 



MnO 



CaO 



M^O 



K 



7-14 



-10 



. 14-03 



20-52 



tr. 



•916 



NaO 



•50 





H 



. -80 





F" 



9 





100-19 



II. Hortonolite Analysis (Warren) 

 Cumberland, B. I. 



III. Hortonolite Analysis (Penfield 

 and Forbes.) Munroe, Orange 

 Co., N. J. 







Eatio 



SiO,.. 



... 33-27$ 



•554 



TiO„ . 



tr. 





Fe„0, 



•37 





FeO.. 



49-32 



•685 



MnO . . 



... 1-50 



•018 



MgO . 



... 16-08 



•402 



H .. 



undet. 





•554 



1-105 



Si0 2 



.... 33-94 



FeO 



47-32 



MnO 



4-32 



MgO 



13-74 



H O 



-48 







99-80 



100-54 



Laboratory of Mineralogy 



Massachusetts Institute of Technology, Boston, Mass., 

 Sept., 1907. 



*Beitrage zur Petrographie der ostlichen Centralalpen, u. s. w., Abh. Kgl. 

 bayer. Akad. Wiss., II, CI. 1894, 18, 651; also shorter papers — Zeitschr. 

 fur Kryst. und Min., No. 26 and Neues Jahrb. f. Min. u. s. w., 1895, Bd. 1. 



