706 MINERAL RESOURCES, 1913—PART II.
sizes
are arranged irregularly; and silk caused by numerous minute parallel
canals or tubes arranged in three directions giving a silky sheen in
reflected light is often present in the natural stones. Corresponding
points in the artificial ruby are that the bubble cavities are
generally perfectly round or only slightly elongated and are never
angular; the color is commonly uniform but when varied is in curved
bands; striations consist of a series of concentric curves; inclusion;.
of foreign particles are generally arranged in curves following the
lines of striations; and silk is never found. A simple jeweler's
microscope and other apparatus useful in distinguishing between the
natural and the manufactured ruby are described and hints are given on
how to make the tests with them. Much of the same information has also
been given on a wall chart showing the same colored plates.
TURQUOISE.
A
very comprehensive work on the ethnology of turquoise has been
published by Berthold Laufer/ associate curator of Asiatic ethnology of
the Field Museum, of Chicago, 111. Dr. Laufer discusses at length the
use of turquoise by the early peoples of India, Tibet, and China. The
esteem in which turquoise was held by these peoplo and the meanings
attached to the wearing of it proves interesting reading.
Another work on turquoise, by J. E. Pogue,2
of Northwestern University, formerly of the United States National
Museum, is in press as this report goes to press. Dr. Pogue's paper
deals with the ethnology, mythology, mineralogy, geology, and
technology of the turquoise, and will prove very instructive on these
subjects.
PRODUCTION.
The
total production of gems and precious stones during 1913 reported to
the Geological Survey amounted to $319,454, or approximately the same
as in 1912. The value of the production has been estimated in part from
the quantities of rough mineral reported aa produced, but the majority
of values have been given by the producers. The production of sapphire
in Montana was the largest ever reported to the Survey and the value is
conservatively estimated at $238,635, or $43,130 more than in 1912. _
This increase was offset by decreases in the output of other gem
minerals, such as spodumene, tourmaline, peridot, emerald, and many
other gems of less importance. The statistics represent as nearly as
possible the first values of the rough mineral. The value of the
finished gem material may several times greater.
i
Notes on turquois in the East: Field Mus. Nat. Hist. Pub. 169, Anthrop.
ser., vol. 13, No. 1, July, 1913. a Turquois: Nat. Acad. Soi., 3d Mem.,
vol. 12,1914.
