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UNITED STATES, CANADA AND MEXICO 199
ornaments
just as they are found, principally at Denver, Colorado Springs, and
other places in the West. Perhaps $1,000 worth a year is disposed of in
this way. The Colorado crystals are compact enough to cut into the
faceted gem known in Europe as " marcasite," which was extensively
mounted in gold during the last century, but has been almost entirely
superseded by the introduction of bright steel jewelry.
Cobaltite,
a sulphide of cobalt, is occasionally cut abroad to be used as a gem
and then resembles a flesh-colored pyrite. It is not found of fair
quality anywhere in the United States.
Little
amber of commercial value has been found in the United States. Though
its occurrence in several places has been noted, the specimens are
believed to be derived from a species of tree quite different from
those which yield the Baltic amber. The earliest description of amber
found in this country is given by Dr. Gerald Troost,1 who
describes two varieties, one opaque, the other translucent, which had
been discovered at Cape Sable, Magothy River, Anne Arundel County, Md.
Both these varieties showed a mixture of the various shades of yellow,
gray, and brown, the colors being sometimes arranged in nearly
concentric zones displaying the most beautiful tints, and sometimes in
alternate bands, spots, dots, and clouds, as in agate or jasper. Some
of this amber was also wax- or honey-yellow. The transparent variety,
which in external appearance resembled colophony gum and had a high
lustre, was sparingly found. The opaque variety is described as " very
dull." Both varieties broke easily and exhibited a perfectly conchoidal
fracture, their hardness being identical with that of the amber found
near the Baltic Sea. Their specific gravity varied from 1*07 to ro8,
the difference being due, in the opinion of Dr. Troost, to small
particles of pyrites with which the cavities were sometimes lined. Some
of the specimens were only slightly electrical, while others exhibited
this quality in a greater degree. Dr. Troost also described a variety
of amber which occurred in fragments or friable, porous masses, of
about the size of a walnut, mixed with iron pyrites, and having a
dull, earthy aspect. These fragments, which were all found in an
alluvial formation,
1 Am. J. Sci. I., Vol. 3, p. 8, Jan. 1821.
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