104 GEMS AND PRECIOUS STONES IN THE
variety
resemble the diamond. An opaque variety of zircon is found in several
localities in the Pike's Peak District, in one instance associated with
amazonstone, and in another with astrophyllite, also with flesh-colored
microline. No material that would cut into gems has been found at any
of these localities. In North Carolina zircon is abundant in the gold
sands of Polk, Burke, McDowell, Rutherford, and Caldwell Counties, in
nearly all the colors peculiar to Ceylon—yellowish-brown,
brownish-white, amethystine, pink, and blue. The crystals are
beautifully modified, but too minute to be of any value. Brown and
brownish-yellow crystals, very perfect in form, occur abundantly in
Henderson County, N. C, and in equal abundance in Anderson County, S.
C. The latter are readily distinguished from the North Carolina
crystals, as they are generally larger, often an inch across, and the
prism is almost always very small, the crystal frequently being made up
of the two pyramids only. Fine crystals of zircon have been found in
Lower Saucon Township, Northampton County, Pa., three-fourths of a mile
north of Bethlehem. The gravels of the Delaware and Schuylkill Rivers
contain considerable quantities of very minute, nearly colorless,
crystals of zircon. Some fine ones, over an inch in length, have been
found at Litchfield, Me., and all through the cancrinite and sodalite
rocks near that place. In the Canfield Cabinet at Dover, N. J., there
are some of the finest known black zircon crystals, over an inch long,
that were found near Franklin, N. J. Opaque green zircons in crystals
an inch long and a half-inch across have been found by C. D. Nimms in
the town of Fine, St. Lawrence County, N. Y. They were remarkable
mineralogical specimens, but of no gem value. One found by Dr. Samuel
L. Penfield, now in the United States National Museum, is nearly 4
inches long and doubly terminated. During 1886, the demand for
minerals containing the rare earths, zirconia, thoria, glucina, etc.,
greatly increased, as they were then wanted to furnish the mantles or
hoods of incandescent gas-burners. This demand led at once to active
search by collectors and mineral-dealers in England, Germany, France,
Russia, Norway, and Brazil, and especially in the United States. So
thorough and successful has this search been that many minerals
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