ORIGIN OF GOLD IN CALIFORNIA. 
617 
Gold has now been detected in almost every kind of rock, 
in slate, quartzite, sandstone, limestone, granite, and serpen¬ 
tine, both in veins and in the rocks themselves at short dis¬ 
tances from the veins. In Australia it has been worked suc¬ 
cessfully not only in alluvium, but in vein-stones in the na¬ 
tive rock, generally consisting of Silurian shales and slates. 
It has been traced on that continent over more than nine 
degrees of latitude (between the parallels of 30° and 39° S.), 
and over twelve of longitude, and yielded in 1853 an annual 
supply equal, if not superior, to that of California; nor is 
there any apparent prospect of this supply diminishing, still 
less of the exhaustion of the gold-fields. 
Origin of Gold in California, —Mr. J. Arthur Phillips,* in 
his treatise “ On the Gold Fields of California,” has shown 
that the ore in the gold workings is derived from drifts, or 
gravel clay, and sand, of two distinct geological ages, both 
comparatively modern, but belonging to different river-sys¬ 
tems, the older of which is so ancient as to be capped by a 
thick sheet of lava divided by basaltic columns. The au¬ 
riferous quartz of these drifts is derived from veins apparent¬ 
ly due to hydrothermal agency, proceeding from granite and 
penetrating strata supposed to be of Jurassic and Triassic 
date. The fossil wood of the drift is sometimes beautifully 
silicified, and occasionally the trunks of trees are replaced 
by iron pyrites, but gold seems not to have been found as 
in the pyrites of similarly petrified trees in the drift of Aus¬ 
tralia. 
The formation of recent metalliferous veins is now going 
on, according to Mr. Phillips, in various parts of the Pacific 
coast. Thus, for example, there are fissures at the foot of the 
eastern declivity of the Sierra Nevada in the state of that 
name, from which boiling water and steam escape, forming 
siliceous incrustations on the sides of the fissures. In one 
case, where the fissure is partially filled up with silica inclos¬ 
ing iron and copper pyrites, gold has also been found in the 
vein-stone. 
It has been remarked by M. de Beaumont, that lead and 
some other metals are found in dikes of basalt and green¬ 
stone, as well as in mineral veins connected with trap-rock, 
whereas tin is met with in granite and in veins associated 
with the plutonic series. If this rule hold true generally, 
the geological position of tin accessible to the miner will be¬ 
long, for the most part, to rocks older than those bearing lead. 
The tin veins will be of higher relative antiquity for the 
same reason that the ‘Ginderlying ” igneous formations or 
* Proc. Royal Soc. 1868, p. 294. 
