This mineral differs from nearly all others held in favor as gems, in
not being transparent and never occurring in the form of well defined
crystals. The opal is perhaps the only other gem of which the same may
be said. In composition Turquois is a hydrous phosphate of aluminum, the
percentages being: Of water, 20.6 per centum; of alumina, 46.8 per
centum, and of phosphoric oxide, 32.6 per centum. Thus in composition as
well as opacity Turquois differs from most other gems, they being
usually silicates or some form of silica. Besides the above ingredients
Turquois always contains a small percentage of copper oxide and usually
iron, calcium and manganese oxides in small amount. It is the copper
compound which undoubtedly gives Turquois its inimitable color, that
color to which it owes its chief charm as a gem. The color varies from
sky-blue through bluish-green and apple-green to greenish-gray.
Of these colors the pure sky-blue or robin’s-egg blue is by far the most
highly prized and is in fact the only standard color for the gem. Green
is, however, the most common and the most lasting color of the mineral,
and it is one of the faults of the gem that the blue shades often fade
to green after being exposed to the light for a time. In a stone of
first quality, however, especially a Persian Turquois, such fading of
color is exceptional. A good Turquois also maintains its color in
artificial light. The hardness of Turquois is 6, in the scale of which
quartz is 7. It is therefore somewhat more easily scratched than other
gems. Its specific gravity varies from 2.6 to 2.8, being about that of
quartz. It does not fuse before the blowpipe, but turns brown and
assumes a glossy appearance. By the copper of the Turquois the blowpipe
flame is usually colored green. When heated in a closed glass tube the
mineral turns brown or black and gives off water. Almost any of these
tests will serve to distinguish true Turquois from stones used to
imitate it. It has a conchoidal fracture and waxy lustre. On account of
its opacity it is almost never cut with facets like most other gems, but
in a round or oval form with convex surface. The pieces desirable for
cutting rarely reach a large size so that big gems of Turquois are
comparatively unknown.
Much of the so-called Turquois used in former times was bone-turquois,
or odontolite, made from fossil bone colored by a phosphate of iron. It
is obtained mostly from the vicinity of the town of Simor, Lower
Languedoc, France. It is sometimes known as Western or Occidental
turquois, in distinction from the Oriental turquois, most of which came
originally from Persia. It does not retain its color by artificial light
as does true Turquois and may be further distinguished by giving off an
offensive odor when heated, owing to decomposition of animal matter.
Further, it is lighter than true Turquois and does not give a blue color
with ammonia when dissolved in hydrochloric acid, as does true turquois.
The finest Turquoises have long come from Persia, from a locality not
far from Nishapur, in the province of Khorassan. Here the mineral occurs
in narrow seams in the brecciated portions of a porphyritic trachyte and
the surrounding clay slate. There are several hundred mines in the
region and the entire population of the town of Maaden derives its
livelihood from mining and cutting the stones. It is said that $40,000
worth of stones are taken from these mines annually. A pound of stones
of the first quality sells at the mines for about $400 and is worth more
than double that price in Europe. There are other Turquois mines in
Persia, but their product is comparatively small. “Persian Turquoises”
have, however, the highest value of all. Other Oriental localities from
which the gem Turquoises are obtained are Sinai, in Arabia, the Kirgeshi
Steppes, in Siberia, and the Kara-Tube Mountains, in Turkestan. Egypt
also furnishes large quantities of Turquois, which does not as a rule
retain its color well.
[Illustration: TURQUOIS.
(New Mexico.)
SPECIMENS LOANED BY FOOTE MINERAL CO.]
Left column:
Indian Amulet.
Artificially polished.
Natural.
Center column:
Waterworn.
Waterworn.
Right column:
Artificially polished.
Artificially polished.
Natural.
Turquois is not an uncommon mineral in the United States and many gems
of fine quality have been obtained from mines within our borders. The
oldest and best known mines are those at Los Cerrillos, New Mexico. This
locality was long worked by Indians and Spaniards, as shown by the great
extent of the excavations. There are pits two hundred feet in depth and
piles showing that thousands of tons of rock have been broken out.
Fragments of Aztec pottery, vases, cooking utensils, stone hammers,
etc., are found at the mines, and trees of considerable size have grown
over the once worked portions. Hence the beginning of the mine workings
must at least date back prior to the discovery of America. The mines
were worked more or less by Spaniards in the early part of the
seventeenth century with the consent of the Indians, or at least without
hindrance from them. In 1680, however, a large landslide occurred on the
mountain at the mine, and many of the Indian miners were overwhelmed.
Believing the Spaniards to be in some way responsible for the accident,
and perhaps fearing that their gods were displeased, the Indians rose in
their might and expelled the Spaniards from the region. It is one of the
few instances in the history of Spanish conquest in America in which the
Indians came off victorious. The Indians seem to have prized the
Turquois highly as an ornament, rudely polishing it and using perforated
pieces like the one shown in the plate for necklaces. They also
decorated their idols and other objects of worship with pieces of
Turquois. The mountain at which the Los Cerrillos Turquois mines occur
is called Mount Chalchihuitl, in allusion to an Indian name that is
supposed to have been applied to Turquois. The mountain is evidently of
volcanic origin. The color of most of the Turquois from this locality is
apple-green rather than the highly prized blue, but some gems of a good
blue have been obtained. Mr. Geo. F. Kunz, writing in 1890 of the sale
of gems from this locality, says that the Indians usually dispose of
them at the rate of twenty-five cents for the contents of a mouth, which
is where they usually carry them. Several other localities in New Mexico
are worked for Turquois. In Cochise County, Arizona, is a locality known
as Turquois Mountain, where considerable mining is carried on. Turquois
is also mined in Gila County, Arizona; Lincoln County, Nevada, and San
Bernardino County, California. Several of these localities have been
opened up recently, the present popularity of the gem perhaps having
stimulated its output.
The much higher price commanded by Turquois of a blue color has led to a
counterfeiting of this color by staining green Turquois or other stones
with Prussian blue.
Mr. Geo. F. Kunz in his “Gems and Precious Stones of North America”
describes a method of detecting this stain. It consists in washing the
stone with alcohol and, after wiping it, to remove any grease, laying it
for a moment in a solution of ammonia, when the blue color, if
artificial, will largely disappear.
At how early a date Turquois began to be prized as a gem is not known.
The word Turquois is a French word meaning Turkish, or a Turkish gem,
and came to be applied because the gem was introduced into Europe by way
of Turkey. It is probable that the gem has been in use from the remotest
past among Oriental peoples and it is certainly still highly prized by
them. Not the least of the reasons for which it is held in high esteem
by them as well as by many Occidental individuals is the good fortune it
is supposed to bring to its possessor. One of the proverbs of the
Orientals is, “A Turquois given by a loving hand carries with it
happiness and good fortune,” and another, “The Turquois pales when the
well-being of the giver is in danger.” Numerous other superstitions
cling around the Turquois. One of these, due probably to slight changes
of color which the stone may undergo under certain climatic influences,
is that if the owner of a Turquois sickens it will grow pale, and at his
death lose its color entirely, but it will regain its color if placed on
the finger of a new and healthy master.
In Germany the Turquois is said to be in much favor for engagement
rings, owing to the belief that if either party prove inconstant the
stone will make the fickleness known by weakening in color. It is
curious that of the two non-crystallized gems, Turquois and Opal, one
should be considered lucky and the other unlucky. Both are more liable
to changes of color than other gems, and this fact has probably led to
the ascription of good or ill fortune to them. In the folk lore of the
months Turquois is connected with the month of December, as the
following rhyme bears witness:
If cold December gave you birth,
The month of snow and ice and mirth,
Place on your hand a turquois blue,
Success will bless whate’er you do.
Oliver Cummings Farrington.