miner, as being the carriers of the quicksilver ores so extensively worked.
Cretaceous Formations.—The
cretaceous formations are geologically very important, especially from
a mining point of view. In the sandstones of the upper part of this
formation occur all the workable beds oi coal yet discovered.
Coal and Cinnabar Deposits.—Cinnabar
deposits have been found in California in many localities and in rocks
of nearly every age—in the Sierra Nevada and in the southern part of
the State, in the triassic strata; in the Coast Ranges, also in the
tertiary. But, so far as known, no valuable bodies of this mineral have
been met with, except in the cretaceous, in which position it is known,
in small quantities at least, in very numerous places, extending in a
line with the metamorphic cretaceous from across the Oregon line in
the north to the vicinity of Santa Barbara in the south.
The
cretaceous formation, principally slates, jaspers, serpentine, and
coarse sandstones, is almost the exclusive one north of Clear Lake; and
south from there to San, Francisco, in which region limestone occurs
quite frequently, it still predominates. South of San Francisco Bay it
forms the central and prevailing mass of the Mount Diablo range,
extending as far as the north end of Tulare Lake, and gradually
yielding to the tertiary. It also constitutes the crest and eastern
side of the Santa Cruz range. In both these chains the cretaceous rocks
are chiefly slates and sandstones, often highly altered, with limestone
in smaller amounts ; and serpentine and jaspers, " which have been
traced unmistakably to their origin as cretaceous shales," are
abundant. South of Tulare Lake the cretaceous formation is local and
comparatively unimportant.
Tertiary Strata.—The
tertiary strata are principally miocene, of marine origin, and for the
most part are not much metamorphosed. They are hardly known north of
