jects
of remarkable beauty, the flashes of red, green, yellow, and blue color
intermingling as the light falls on them. A beautiful opal was
exhibited by the Mexican Commission, at the World's Fair held at
Philadelphia in 1876, and was very greatly admired by visitors.
An opal from Zimapan, Mexico, was analyzed by Klaproth, with the following result:
Silica............................................. 92-00
Peroxide of Iron................................... 0-25
Water............................................ 775
The
noble opals at Esperanza are remarkable for the extent and intensity of
their reflections. The harlequin opals are noted for the diversity and
the small size of their colored spots, which form beautiful miniature
mosaics. One of the most pleasing varieties has a play of red fire
like the red variety from Zimapan, and mingled with it flashes of
brilliant metallic emerald-green, and occasionally a violet-blue of
remarkable intensity. One of the red varieties from the Rosario Mine,
on the hill of Jurado, has a violet-blue reflection of peculiar beauty;
and the same mine produced a variety with a metallic emerald-green and
a dark ultramarine color combined, or rather showing, one after the
other. The lechosos opals, as those with the red and green reflections
are called in Mexico, are very common on the hill of Peineta, and less
plentiful in the other mines of Queretaro. The opal mines of Esperanza
are situated ten leagues northwest of San Juan del Rio, in the State of
Queretaro, and are very extensive, having been traced over a district
thirty leagues long and twenty leagues wide. They were discovered in
1835, on the landed estates on which they are situated, by a farm
laborer. It was 1870 before a settlement was made on the edge of the
mountain Ceja de Leon, by Jose Maria Siurob, near the present mine of "
Santa Maria Iris." In 1873 Dr. Mariano de la Barcena1 made a
special report on this opal district, in which he states that he has
discovered ten veins, or mines, as they are called. He says : " The
opals of Esperanza are found forming chains more or less regular, on
the banks of porphyry in quartz which forms its base, or disseminated
through the mass of the
1 Am. J. Sci. III., Vol. 6, p. 466, Dec., 1873.
