BULL. GEOL. SOC. AM. 



VOL. 12, 1900, PL. 32 



Figure 1. — Exposed Surface of Graywacke and Graywacke Slate near Thomson, Minnesota 



Figure 2. — Guawvacke with Contorted Quartz Vein, Cari/ion, Minnesota 

 GRAYWACKE SLATE AND GRAYWACKE 



