FACTS Iff AMERICAN MINING. 77 



slate. The gold-bearing belt, east of the copper belt, is character- 

 ised by quartz ledges traversing slates, limestones, sandstones, 

 and granite. Crossing the crest of the Sierras we come into regions 

 where the gold is alloyed with silver, and further east it is entirely 

 replaced with silver, associated with copper, antimony, and arsenic 

 ■ — all the metals and minerals being pretty distinctly characterised 

 in their distribution by the nature of the rocky strata and condi- 

 tion of metamorphism. 



The age of the gold-bearing rocks in California has not been de- 

 termined, but a considerable portion are distinctly carboniferous. 

 In the coast mountains gold is found in close proximity to rocks 

 of a tertiary age ; and the fact of gold being occasionally found in 

 cinnabar-bearing formations, leads to the belief that it is even as 

 recent as the miocene (or middle tertiary), in opposition to 

 existing views. 



Professor Silliman records the examination of some mines in 

 the neighbourhood of Fredericksburg, and states that the gold- 

 bearing quartz usually exists in talcose and mica slate ; that in 

 the greater number of cases the eye discerns no gold, though 

 sulphides of iron, zinc, and lead are often seen. In the Moss 

 Mine, quartz which yielded gold to the value of £20 to £40 per 

 ton showed no sign of gold, even with a magnifier, thus proving 

 that we cannot judge of the gold-bearing capabilities of quartz 

 by the sight. In the Walton Mine a more notable instance of 

 this occurred — firm and compact quartz, interspersed with iron 

 pyrites and dark iron ore, gave on first trial £16 per ton, second 

 trial £32, third trial £80, fourth trial over £500 to the ton ; but 

 in the first three trials gold was not visible to the eye. 



Professor Eogers ascertained that the talcose rock underlying 

 a quartz vein was itself gold-bearing to a depth of 6 inches. 

 What other rocks enclosing gold-bearing veins are also auriferous, 

 and to what extent, we have still to learn. * 



The distribution of metallic wealth in Western America occurs 

 as follows, viz :-In Pacific Coast Eange on west, occur quicksilver, 

 tin, and chromic iron. In Sierra Nevada belt on west slope there 

 are two zones ; the foot hill chain, copper mines ; a middle line of 

 gold deposits east of this line ; and the east base of Sierra Nevada, 

 striking into Mexico, silver mines with but little base metal. 



Through New Mexico, Arizona, Middle Nevada, and Idaho, 

 another line of silver mines exists, with complicated association 

 of base metals. 



Through New Mexico, Utah and Western Montana, argenti- 

 ferous galena lodes. 



To the east again, the New Mexico, Colorada, Wyoming and 

 Montana gold belt is exceedingly well defined. 



* At the Caledonian Reef, in New Zealand, the footwall adjacent to the shoot of gold was 

 itself found to be gold-bearing for a thickness of 15 feet, that portion of the enclosing roc ^ 

 having been crushed with profit. 



