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use
for large marbles was once quite common, but glass marbles of the same
size, and still called "agates," are now generally substituted. In fine
mechanical work, such as bearings for delicate instruments, and in
tools for polishing and grinding, agate is still extensively used.
Various
curative properties were formerly attributed to the agate, belief in
some of which still survives, especially among Mohammedan peoples. It
was regarded as a cure for insanity, and as a preventive of skin
diseases. It symbolized health and wealth, and was supposed to render
its wearer gracious and eloquent.
Onyx and sardonyx are
varieties of agate in which the layers are in even planes of uniform
thickness. This structure enables the stone to be used for engraving
cameos. As is well known, these are so made that the base is of one
color and the figure of another. This art of making cameos reached a
high degree of perfection among the Romans, and many superb examples of
it have come down to us. The word onyx means a nail (finger-nail), and
refers to some fancied resemblance, perhaps in luster, to the human
nail. Sardonyx is a particular variety of onyx in which one of the
layers has the brown color of sard. Other kinds of onyx are those known
as chalcedonyx and carnelionyx, in reference to the color of the
intervening layers. So-called Mexican onyx is composed of quite a
different mineral from the onyx here considered, it being made up of
calcite rather than quartz. Hence Mexican onyx can be scratched easily
with a knife, while quartz onyx cannot. Mexican onyx has, however, the
banded structure of quartz onyx, and it is in allusion to this
undoubtedly that the name has been applied. A sardonyx upon which Queen
Elizabeth's portrait was cut constituted the stone of the famous ring
which she gave the Earl of Essex as a pledge of her friendship. It
will be remembered that when the earl was sentenced to death he sent
this ring to his cousin, Lady Scroop, to deliver to Elizabeth. The
messenger by mistake gave it to Lady Scroop's sister, the Countess
Nottingham, who being an enemy of the earl's did not deliver it to the
queen, and the earl was executed. On her deathbed the countess is said
to have confessed her crime to the queen, who was so infuriated that
she shook her, saying " God may forgive you, but I cannot."
In
the Middle Ages sardonyx was used as an eyestone, and is employed in
Persia to this day for the cure of epilepsy. It was supposed by the
ancients to be an entirely different stone from the onyx. To it was
ascribed the property of conferring eloquence upon its wearer, and it
especially symbolized conjugal bliss. It is mentioned in Revelations
as one of the stones forming the foundations of the Holy City. Onyx and
sardonyx which come from the Orient are esteemed of much higher value
in trade at the
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