34 



WILLIAM J. MILLER 



mouth of Two Brooks near Goldsmith. A lens of silexite was 

 there pulled apart in the magma, some of which flowed into the 

 intervening space. Contacts are sharp, and highly foliated granite 

 occurs only close to the silexite. 



Some interesting masses of silexite of relatively late origin 

 occur in slightly foliated quartz syenite on the hill half a mile north 

 of Mud Pond near Riverview. South of the summit of this hill 

 several dikes of silexite contain very little feldspar, and they 

 lie parallel to the foliation of the syenite, without sharp contacts. 

 About 40 rods east of the summit of the hill a pegmatite dike 10 



Fig. 4. — A mass of silexite 28 feet long with branching dikes in the granite on the 

 ridge one and two-thirds miles north-northeast of Union Falls in the Lyon Mountain 

 quadrangle. 



inches wide and 15 feet long grades into the quartz syenite on either 

 side and lies parallel to the foliation. The middle of the dike or 

 segregation mass is nearly pure siHca (silexite) which grades into 

 the pegmatite. Near by a coarse-grained pegmatite dike several 

 feet wide cuts obHquely across the foKation, this dike therefore 

 belonging with the latest pegmatites below described. 



Figure 5 represents a small portion of a belt of granite 25 to 

 30 feet wide and 100 feet long which contains many angular inclu- 

 sions of silexite and Grenville quartzite and schist. All the inclu- 

 sions have sharp contacts, and they mostly have their long axes 

 roughly parallel to the magmatic flow-structure foliation which 

 tends to curve about them. Masses of nearly pure silexite of very 

 early origin were here pulled to pieces, and the pieces were moved 

 in the still fluid granite. 



