Plate 20 



A. Syenite from Scotts Cobble, containing microper- 

 thite (M), brown hornblende (Hb), and quartz (Q). 

 Crossed nicols, actual field 0.08 inch or 2.0 mm. 



B. Plumose border of bostonite dike on the left, 

 against Grenville gneiss on the right. Crossed nicols, 

 actual field 0.08 inch or 2.0 mm. 



