CALIFORNIA.
Although the yield of the gold deposits of California has from various causes greatly fallen off during the decade, this State still holds the first rank as a gold producer. The original source of the gold of California is found in the quartz veins occurring in a highly metamorphosed series of rooks, of both sedimentary and eruptive origin, steeply upturned against the west flank of the great granite bodies of the Sierra Nevada, and generally known as the gold belt or auriferous slates. By their great alteration the fossil casts of the sedimentary series have been so largely obliterated that their exact geological age has been almost impossible to determine. The first recognizable fossils found in them were considered to be of Jurassic age, but more detailed studies of later years have extended the possible age of the gold-bearing sedimentary rocks downward into the Paleozoic acid upward into the Lower Cretaceous. The eruptive rocks are intrusive diorites and diabases, in some cases altered into serpentine. Besting unconformably upon the auriferous slates along the foothills are beds of'later Cretaceous age which contain no original deposits of gold.
For something over 100 miles northward from what was originally considered as the southern limit of the gold belt proper, the quartz veins follow the apparent strike of the slates in a north and south direction, parallel with the general trend of the range, and form a regular and definite line, which is known as the Mother lode. These veins are generally in the sedimentary rocks, sometimes at the contact of intrusive bodies. Their principal metallic constituents are free gold and auriferous pyrites, with insignificant amounts of other metals. The abovementioned characteristics hold good for a majority of the veins in the gold belt, but there are many variations from them, especially in the middle region from whose disintegration the richest placers were derived. The veins sometimes trend east and west and are entirely inclosed in eruptive rocks, in which case their mineral constituents are more varied and include some silver and base metal ores. In other cases they show a tendency to follow in the sedimentary beds a direction parallel with the contact of inclosed eruptive bodies, and again cross from the former into the latter. A certain belt of diabase is characterized by the occurrence of copper ores.
