The
carnelian is found in nodular masses, and often as rolled pebbles ; at
Baroach, in India, pebbles of great beauty are found, also in the
riyers of Uruguay. It is largely cut and used for rings, seals, watch
pendants, beads, and other ornaments. By artificial treatment its
beauty can be greatly enhanced. As noted above, the sard is only a
yellowish brown carnelian. Specimens from India are of great beauty,
while those obtained from the neighbourhood of Babylon were by the
nations of antiquity esteemed as of great value. The different
varieties of chalcedony are common in this Colony, although rarely of
good colour.
Chrysoprase
is
an apple green chalcedony, its green colour owing to oxide of nickel.
Although mentioned in the writings of antiquity, it is doubtful whether
the stones were identical with those of modern times, because no works
o£ ancient times have come down to us in true chrysoprase. It is found
in Silesia embedded in serpentine, and was at one time in great request
in Prussia, the kings only allowing the mines to be opened once in
three years, and they then kept the finest specimens for themselves.
Frederick the Great used the chrysoprase in adorning the Palace of Sans
Souci. It was also used for the interior decoration of the walls of St.
Wenzel's Chapel, in the Cathedral of Prague, which was built in the
fourteenth century. In the Royal Palace of Potsdam there are two tables
formed from chrysoprase, which are 3 feet long, 2 feet broad, and 2
inches thick. A very fine intaglio of light green chrysoprase, and of
oval shape, representing the head of Ariadne, is in the Hope collection.
The
chrysoprase takes a high polish, is really a very pretty stone, and has
the advantage of being found in large pieces. During the last year or
two, attempts have been made to revive the taste for this stone for
ornamental purposes, but they have only partly succeeded. Klaproth the
chemist, was the first to discover the presence of nickel in
chrysoprase, and also the fact that the stone contained a small
quantity of water. If by the influence of heat the water is removed,
the beauty of the stone is destroyed ; for this reason it is supposed
that the nickel is present in the form of a hydrate. The working of the
stone has to be done with great care, on account of the ease with which
the colour is partly destroyed; it is principally cut en cahochon, with
small facets round the edge of the upper side. The greater number of
cut stones of chrysoprase are done at Warmbrunn, in Silesia. At
Oberstein a green colour is artificially given to chalcedony by means
of the salts of nickel, or of chromic acid, it then having the
appearance of chrysoprase. The value depends on the colour and its
freedom from flaws. Besides the locality mentioned the chrysoprase is
found in America, principally in a vein of serpentine, in the nickel
mines at Nickel Mount, near the town of Kiddies, Douglas County,
Oregon; it is found here in veins over an inch in thickness, and stones
several inches square could be made from it. The colour is good. The
name signifies " golden leek," and is in reference to its colour.
Stones much resembling the chrysoprase are prase and plasma, the
former being translucent in appearance, and of a muddy olive-green
colour. The name is from prason, signifying a " leek," and was also
given on account of its colour. Plasma is a translucent variety
of chalcedonic quartz, of a brighter green than prase. The name
signifies " image," or anything formed or imitated. It is found in
ancient ruins, and was no doubt confounded with the chrysoprase. It is
often speckled with white.
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