GOLD IN SOUTH AFRICA AND AMERICA. 61 



gneissic and other metamorphic rocks, in seam diggings of 

 decomposed bed-rock with irregular seams of auriferous 

 quartz. (Fig. 1.) In Placer county the lodes running E. 

 and W., also N. and S., traverse syenite, also metamorphic 

 slate. In Nevada county certain lodes run N.W., and also 

 N.E., the country rock being granite, greenstone, and slate ; 

 generally speaking, the lodes run through metamorphic 

 schists, or greenstone, alternating with belts of syenite. 



In the Rocky Mountain regions (Colorado, Montana, Da- 

 kota, New Mexico, &c.) placers and auriferous lodes are 

 plentiful. As a rule the lodes run through granitic rocks 

 and metamorphic schists and slates, gneiss and quartzite, 

 the gold being associated with iron pyrites, galena, blende, 

 silver ore, &c. So, too, elsewhere in North America. Gold 



FIG. 40. SKCTIOX OP A PART OF TABLE MODSTAIX (CALIFORNIA). 



is sometimes found as a telluride (in Colorado, &c.), at 

 Boulder in lodes through micaceous schists, gneissic granite, 

 c., between granite and porphyry. Also in West Austra- 

 lia, New Zealand, Transylvania, Hungary, &c. 



At Cripple Creek, Colorado, some lodes run through 

 andesite. At Telluride, Colorado, some gold and silver- 

 bearing veins are in rhyolite, augite-andesite, andesite 

 breccia, &c. 



A t Silver Cliff, Colorado (Bassick Mine), zones of various 

 sulphides surround pieces of country rock, and carry silver 

 and gold, Tellurides, too, occur. 



