utilized
as gem stones. Fine agates and jaspers are found about the Willamette*
Columbia, and other rivers in Oregon. Beautiful red and yellow
carnelian and sardonyx result from the silicification of the corals and
sponges at Tampa bay, Florida, and although the pieces are not large,
the colors being natural are very good.
The
silicified bones of the atlantasaurus found at Morrison, Colorado, have
at times a coarse cellular structure, infiltrated with carnelian,
giving a very pleasant effect of a brilliant red striped and mottled
appearance.
Chalcedony
coats and incloses the crystallized cinnabar of the Eed-ington and
other mines of California; and these crusts, if cut with the cinnabar,
form very pretty and interesting gem stones.
Silicifled coral.—The
true silicifled corals found at Schoharie, New York, along the
Catskills, and at a large number of other American localities, form
very pretty gem stones. Some similar to the so called fossil palm wood
from India have been observed at a few localities in New York State.
One very interesting black siliceous coral form with large white
markings was found at Catskill, New York; when cut across the large
white columnar lines the effect was very pleasing and ornamental.
Silicifled wood.— In
the valley of the east fork of the Yellowstone river, and in the
volcanic Tertiary rock, which here attains a thickness of 5,000 feet
and is made up of fragmentary volcanic products which have apparently
been redistributed by water and now form breccias, conglomerates, and
sandstones, Mr. W. H. Holmes(a) mentions the occurrence of silicifled
wood in great abundance, and in some cases the trunks are in situ in these strata.
In
the valley of the main Yellowstone, in the Gallatin range, and about
the sources of Canon and Boulder creeks, also near the divide at the
head of Boulder creek, and at a number of points above this line, may
be observed trunks many feet in height and of gigantic proportions,
standing in the identical strata in which they grew. In general, these
strata are horizontal. Three miles south of Gardiner's river, at an
elevation of 6,000 feet above the sea, silicifled trunks are found in
sandstone belonging to the same strata. On the south side of Third
canon, opposite the mouth of Hell-roaring creek, is a massive
promontory, in which many fine trunks are exposed in a conglomerate. At
Amethyst or Specimen mountain some of these trunks have been found 10
feet in diameter. Many thousands of silicifled trees are found ; in
some cases the structure is well preserved, and in other cases
completely agatized or opalized, and lined with crystals of calcite,
quartz, and beautiful amethysts. In this locality many of the finest
specimens of American silicifled wood are found.
The workmen on the Denver and New Orleans railroad in 1882(b),
a "Geology of the Yellowstone National Park," page 48. b A. E. Foote, Naturalist's Leisure Hour, July, 1882, page 32.
