|
 |
 |
|
Sardonyx (banded agate). The specimen is 2.5 cm (1
inch) wide.
|
Onyx from Australia
|
Onyx from Brazil
|
Onyx is a cryptocrystalline form of quartz. The colors of its bands
range from white to almost every color (save some shades, such as
purple or blue). Commonly, specimens of onyx available contain bands of
colors of white, tan, and brown. Sardonyx is a variant in which the
colored bands are sard (shades of red) rather than black. Pure black
onyx is common, and perhaps the most famous variety, but not as common
as onyx with banded colors. Sardonyx (banded agate). The specimen is
2.5 cm (1 inch) wide.
It is usually cut as a cabochon, or into beads, and is also used for
intaglios and cameos, where the bands make the image contrast with the
ground. Some onyx is natural but much is produced by the staining of
agate.
The name has sometimes been used, incorrectly, to label other banded
lapidary materials, such as banded calcite found in Mexico, Pakistan,
and other places, and often carved, polished and sold. This material is
much softer than true onyx, and much more readily available. The
majority of carved items sold as 'onyx' today are this carbonate
material. |
|
