BULL. GEOL. SOC. AM. 



VOL. 12, 1900, PL. 34 



» 



Figure 1. — Microphotograph of Kigatjd Hornblende-Syenite 



Dark mineral is biotite and the white is quartz. Strong allotriomorphism of biotite 

 towards the feldspar is well shown. Ci'ossed nieols X 38 



Figure 2. — Microphotograph of Rigaud Quartz Porphyry 



Quartz phenoeryst shows crenulated border due to secondary growth 

 Crossed nieols X 47 



RIGAUD HORNBLENDE-SYENITE AND QUARTZ PORPHYRY 



