Heliotrope
has been greatly admired in modern times; its price depends upon the
color and quantity of red spots contained in ft. From one to twenty
dollars is the usual price for good and large specimens.
It
is said that superstitious people in the middle ages valued the
heliotrope, with many red spots, very highly, thinking that Christ's
blood was diffused through the stone.
AGATE.
This
stone was well known to the ancients, under the name of achates, and
was used for various purposes of jewelry. In Rome, it was principally
used for cutting cameos from the striped kind, the onyx. It has also
been worn as an amulet, with different characters engraved upon it. Its
name is derived from a river in Sicily, where the ancients procured it.
Agate is a mixture of several species of quartz, which are variously
combined; chalcedony or carnelian usually forms the principal part, and
is mixed with horn-stone, jasper, amethyst, quartz, heliotrope,
cachelong, and flint; and according to the predominating substances, it
is sometimes called chalcedony, jasper, or carnelian agate. Its color,
as well as its other characters, depends upon the nature of the mixed
parts ; likewise its hardness ; but it usually scratches white glass,
and has a specific gravity of 2-58 to 2-66 at the utmost.
According to the different figures represented in agate, it receives its various names.
1st. Ribbon, or striped agate, representing layers variously colored, and alternating with one another. Onyx, or
agate onyx, are such agates as have the colors beautiful and distinct,
and whose layers run in a parallel direction with the larger surface ;
whereas the common ribbon agates display their various layers on the
surface, without being
