ico
to imitate the ancient objects, to meet the demand of visitors to that
country. This material is entirely stalagmatic in its formation, and
yellow-brown and red oxides of iron have been deposited between the
layers. It is generally cut across the layers, which gives it a
beautiful veined appearance. When it is cut in the same direction as
the deposition, the botryoidal structure is well shown, the mineral
being so translucent that the markings resemble colored clouds. It is
one of the most beautiful ornamental stones of any age, and has been
used extensively for ornamental purposes in Europe as well as in the
United States, where it was first introduced about 1876, when it
brought about ten times its present price. The natives in the vicinity
of Pueblo sell large quantities of this material, made into trays,
crucifixes, reliquaries, inkstands, penholders, paper-folders, and
paperweights, in the form of single fruits or bunches of fruit, fish,
or other natural objects, which are copied, not only with regard to
form, but often with remarkable skill in the utilization of the colors
in the stone. So great is the variety of tints of color in which the
material is found that there is scarcely a limit to its possibilities
for such purposes. Bernardino de Sahagun refers to iztac chalchihuitl,
white or fine green, and quite transparent, obtained from quarries in
the vicinity of Tecalco, which Dr. Daniel G. Brinton ' believes to be
the modern Tecali; and the description and locality answer so well to
those of our so-called Mexican onyx that there can scarcely be a doubt
that this was referred to by Sahagun as iztac chalchihuitl.
In
the summer of 1888, William Cooper, of Esperanza, discovered in the
volcano of Zempoaetepetl, in southern Mexico, a deposit of a beautiful
mineral, which has received the trade name of mosaic agate; this is
really the so-called Mexican onyx. It is an aragonite, with the
difference, however, that the latter is always veined or stratified,
whereas the new material is a brecciated or "ruin aragonite." The
original formation has evidently been entirely broken up, the fragments
having been cemented together and the crevices all filled in with a new
deposition of aragonite, showing conclusively that a deposit of
Mexican onyx had been fractured by some disturbance, possibly vol-
1 Science, Vol. 12, p. 168, Oct. 5, 1888.
