296 GEMS AND PRECIOUS STONES IN THE
safely
estimated until after it has been cut by the lapidary." Possibly these
opals had been soaked in oil, a device which is sometimes practised to
improve or restore the color.
About
one hundred natives work the Esperanza mines in a desultory manner. The
opals are nearly all cut at three cutting establishments, in the city
of Queretaro. The cutting is done in the rudest manner, by native
lapidaries, who neither give the •stones a good shape nor polish them
properly ; hence they rarely show their true beauty, and very few are
sent out of Mexico to be cut. Fully 50,000 are cut annually, and this
amount could be doubled should the demand exist. Occasionally, when the
color is thick enough, they show an intensity of color—often only one
color, such as red, green, or yellow—not rivalled even by the Hungarian
stones, and the Mexican opal in all its varieties is often purchased
with the hope of realizing for them an equal value. The prices asked
vary from a few cents to upward of $100. Lots of thousands are often
sold for less than ten cents each, occasionally exceptional stones
selling for $100, rarely for more. A beautiful series of opals
exhibited by the ' Mexican Commission at the World's Fair held in Paris
during 1889, consisted of noble and fire-opals. One large stone with
superb pink flames was especially beautiful.
A
remarkable fire-opal was brought home from Mexico by Alexander von
Humboldt, and is still preserved in the Berlin Mineralogical Museum.
The
Spanish historians, in their marvellous stories of the wonders seen in
Mexico at the time of the Conquest, describe the image of the mystic
deity, Quetzalcoatl—God of the Air—on the great pyramid of Cholula, as
wearing a mitre waving with plumes of fire, an effect which is supposed
to have been produced by masses of mosaics of fire-opal. A well-known
Mexican opal is the one sold in the collection formed by Henry Philip
Hope.1 It was a Mexican fire-opal, or sun-opal, as it was
called, carved with the head of the great Mexican Sun God, and is
believed to have been taken from a Persian temple. It has been known
since the sixteenth century, and brought
262 at the sale of the Hope jewels in London in 1886. With the fire-opal is also
1 Catalogue Hope Collection, plate xxxi, fig. 3, p. 3 (London, 1839).
