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GEMS.
III.
AGATE.
So called from the Latin name, Achates
of the
Sicilian
river now called Drillo, on whose shores this substance is found. This
term generally indicates a great variety of semi-transparent quartzes.
Agates are found in almost every part of the earth. Some are found in
the East, some in the West, and the difference of their constituent
parts makes the specific weight vary from 2-5891 to 2-6901.
The
agate, properly so called, like that of Sicily, is naturally
translucent; less transparent than crystalline quartz, but yet less
opaque than jasper: it is too hard to be scratched even by
rock-crystal; it takes a very good polish; it is never found in regular
forms, but always either in nodules, in stalactites, or in irregular
masses. Nevertheless, the agate called chalcedony frequently
crystallizes in rhomboids. The Sicilian agate is often of a pale or
grey colour, veined in a variety of forms; sometimes it is spread in
reddish-violet spots.
The
" fasciatella" agate is like a sample of many agates united in a single
piece, and disposed in bands close to each other like ribbons or belts.
The bands are sometimes in right lines; others are curved, and then of
a circular form arranged round a common centre.
Eye agates consist of those parts of the stone in which
