The
gold deposits of the Caucasus, though immortalized in the tradition of
Jason and the Argonauts, are now entirely abandoned, the last attempt
at working them having been suspended in 1875-
In
India gold is obtained in small quantities by native gold-washers in
various parts of the highlands of southern Bengal, and more recently
quartz veins and alluvial deposits of considerable promise have been
discovered in the district of Wynaad, in the southern part of the
Madias Presidency.
On
the Atlantic slopes of North America, the chief gold-bearing localities
are on the Chaudiere river, near Quebec, and in Nova Scotia. In both
instances the quartz veins worked are contained in slates belonging to
the Quebec group of the Lower Silurian period, those of the latter
province being specially remarkable for their quasi-stratified
character, as they penetrate the slates at a very low angle of
inclination, and have been folded and corrugated together with the
containing rocks by subsequent disturbances. Other deposits of old
geological periods are found in Tennessee and North Carolina.
On
the Pacific side of America gold is found under very different
conditions and on a much larger scale than on the Atlantic side. The
whole distance from Mexico to Alaska may be said to be more or less
auriferous, the most extensive deposits being in the great
north-and-south valley of the Sacramento, which runs parallel to the
coast, between the so-called Coast Mountains and the Sierra Nevada, the
latter being distinguished further to the north in the Cascade range.
Others of less extent are known in the Klamath, Columbia, and
Fraser River basins; they extend in the last two far back into the
interior to the region between the Cascade range and the Rocky
Mountains. In many of these valleys alluvial deposits are developed to
an extent unparalleled elsewhere, the river channels being bordered by
banks or benches of gravel and sand, rising in terraces to considerable
heights on the flanks of the hills. For example, at the Methow, a
tributary of the Columbia, there are sixteen lines of such terraces the
highest about 1,200 feet above the river; and at Colville, on the
Columbia, traces of old terraces, much degraded by frost and rain, are
seen at 1,500 feet above the river. These gravels, which are of
Pliocene and more recent origin, are in many places, though very
unequally auriferous, the richest points being found in the bars or
shingle banks of the river after the summer floods, and in the channels
of the smaller tributary streams, where the poorer material has been
partially enriched by a process of natural washing. The most extensive,
or rather the best known because most completely explored, deposits of
this class are those of the Upper Sacramento Valley, in California (see
vol. iv., p. 701). (a) Others of considerable importance are
worked in the Cariboo district on the Upper Fraser River, yielding very
coarse gold. Another discovery of a singular character, the produce
being a regular gold gravel, was made some years back at Salmon River
in Oregon, but the deposit, though exceedingly rich, was soon
exhausted. Gold-bearing quartz veins are also common over a large part
of California, notably in Grass Valley (vol. iv.. p. 702), in strata
that are supposed to be of Triassic age, the associated minerals being
iron and arsenical pyrites, galena, &c. In Calaveras county,
tellurium ores like that of Transylvania are characteristic of the
gold veins. In the adjacent States of Nevada and Colorado, gold is so
intimately associated with silver ores, that it is for the most
part only obtained from the ultimate process of refining the reduced
silver. The same remark applies to the most of the mines of Mexico, and
on the south-west coast of America, in Peru, Bolivia, and Chili. (See Silver.)
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