Geological researches in China, Mongolia, and Japan, during the years 1862-1865.

CHINA, MONGOLIA, AND JAPAN. 91
The only formation seen was the terrace deposit, till near the divide, when an
obscure green wacke was found in place, and near this a greenish-black amygdaloid.
Large blocks of granite were also seen here, and this rock is probably in place
near by.
Descending to the west we entered the valley of the Toshibetz, a large creek,
navigable with small, flat boats, and soon reached the gold washings of Kunnui.
This part of the valley occupies a broad depression, perhaps 15 miles long by 7
broad, and raised several hundred feet above the sea. It has been filled with the
recent terrace deposit, and subsequently eroded in part, after which an extensive
deposit of auriferous gravels, etc., has taken place over at least a considerable part
of the area.
In one of the side valleys the older rocks are exposed, and here the gold bearing drift was found resting, in different places, on an argillite similar to that seen at
Washinoki, and containing the same vermiform fossils, in strata striking N. 85~ W.,
and dipping 500 northerly, and on an amygdaloid similar to that on the divide.
Not far from here the terrace deposit overhangs the creek in a high bluff. Out
of the base of this precipice I obtained a number of well-preserved fossil shells. In
the same bed were found Ostreae, Pecten, Scalaria, Terebratula, Nuculina? Serpula?
Corals, Bryozoa, and fragments of a thick shell with cross-fibrous structure. Some
of the shells retained, at least in part, their organic matter and nacreous lustre,
and one species of Pecten appeared to be identical with a species living in the
adjacent seas.
At one end of this bluff is a large rock of the amygdaloid in place, which has
been exposed by the erosion of the terrace deposit, and on it are incrustations of
Serpulae.
This amygdaloid contains masses of a green rock resembling jasper, in which are
scattered flakes of native copper. Blocks of manganese (binoxide) in the immediate
neighborhood seem also to have come from the amygdaloid.
The auriferous gravel occurs along both sides of the river in the form of a plain,
which descending gently from the hills faces the stream with a bluff. The whole
district appears to have been worked in former times, though when appears to be
unknown. Broad and deep canals of considerable length were dug to bring water
from up the creek, and a well arranged system of "ditch diggings" seems to have
been carried on. All these workings are covered with a dense growth of trees,
apparently not differing from the surrounding forest; some seen in the ditches being
as much as eighteen inches in diameter. The method of washing the gold does not
seem to have differed from that now used by the Japanese.
The principal rocks, that have contributed to form the auriferous drift, are varieties of granite, chloritic and micaceous schists, quartzites, and amygdaloid, with
geodes of chalcedony from the last mentioned rock. Rolled fragments of binoxide
of manganese are frequent also, perhaps derived from the amygdaloid. The concentrated sand of the washing is principally magnetic iron associated with zircon
sand.
The manner of working the deposit is ingenious, and will be understood by
referring to the annexed diagrams.