and
of a sulphate. Lapis-Lazuli fuses with great difficulty, and expands
before the blow-pipe, after which it becomes a porous, colourless glass
; but if heated with saltpetre, it turns to a beautiful green.
In
the Cordilleras, near the sources of the Cazadero and Vias—little
tributaries of the Rio Grande— not far from the high road leading to
the Argentine Republic, and a short distance from the great watershed
in the Chili dominions, the Lapis-Lazuli is found in a thick stratum of
carbonate of lime, accompanied by small quantities of iron pyrites.
Lapis-Lazuli
is also found in Siberia, on the shore of the Shudank, particularly on
the lands near the Baikal Lake, into which that river empties itself.
Marco Polo, in his travels to the princes of Tartary in 1271, found it
in the upper district of the Oxus, mixed with iron ore, whence the
Armenian merchants still bring it to the market of Orenburg, in Eastern
Russia. In many provinces of China, and in Bucharia, it is found in
granular limestone with iron pyrites, and, on the banks of the Indus,
in a greyish limestone.
In
Italy it is a favourite stone for ornamenting churches, and in the
chapel of San Martini, at Naples, the Lapis-Lazuli is profusely
employed not only for decorative work, but even as a structural
material. In the Zarskoe Palace, near St. Petersburg, there is an
apartment, called Catherine II.'s chamber, formed entirely of
Lapis-Lazuli and Amber.
This
stone was in early times much valued, because it was the only material
from which the true ultra-marine of the artist, so celebrated for its
effect and permanence, could be obtained. Artificial ultra-marine is
now prepared
