Hawkins — Notes on the Geology of Rhode Island. 469 



connected with granitic intrusions might have caused the 

 formation of the original silicate minerals from which the 

 steatite must have been formed. In the writer's opinion 

 the steatite, and the limestones associated with it, at least 

 the smaller limestone masses, are the product of subse- 

 quent alteration of earlier silicates of magnesia and lime 

 which were formed in connection with the intrusion of the 

 granite, replacing portions of the schist. An analysis of 

 the fine-grained gray steatite of this type is hereby given 

 (Table III, analysis 20). This rock is closely associated 

 with a coarser phase which has a groundmass principally 

 composed of fibrous talc and steatite with a little calcite, 

 in which are embedded black, lustrous ankerite crystals. 

 5 mm. in diameter, with bright cleavage. This latter 

 phase shows the mineral composition to be expected in 

 the finer grained mass analyzed. A recast from the 

 analysis to form these minerals gives the following 

 results : — 



Recast of Chemical Analysis of Steatite from Manton, 

 (Analysis 20.) 



S. I. 



Ankerite 



Magnetite 

 Pyrite 



S Calcite 

 \ Siderite 



410% 

 3-37 



4-73 



•02 



12-22% 



SiO, 



AlA 

 Feb 



MgO 



Soapstone |N - 



Matrix ] K 5 



t 



Total 



= 55-39% ] 



= -04 | 



= 4-04 | 



= 26-63 A - - 



oo ! An aggregate of green schist. 



= -46 | 

 = 1-23 



partly changed to talc. 



88-17% J 

 100-39% 



Of the soapstone matrix (88-17%), the amount of water 

 present therein (1-23%, compared with 4-80% in talc), 

 indicates that talc forms 25-64%. 



The soapstone analysis (20) when compared with that 

 of the unaltered schist (analysis 12), shows changes 



