Agate, Amarillo Stone, Amberine, Azurchalcedony,
Basanite, Bayate, Beekite, Binghamite,
Bloodstone, Blue Chalcedony, Buhrstone, Carnelian, Chrome-Chalcedony,
Cubosilicite, Dallasite, Damsonite, Darlingite, Diackethyst, Herbeckite, Irnimite,
Jasper, Keystonite Chalcedony, Kinradite, Myrickite, Onyx,
Quetzalitztli, Sard, Sardonyx,
Schlangenhautachat, Seftonite, Vogelaugenachat,
Vogelaugenjaspis, Wilkite, Youngite
a translucent, usually grayish blue, variety of cryptocrystaline,
or fine-grained, Quartz
with a fibrous microstructure. Chalcedony has traditionally
been defined as a fibrous cryptocrystaline variety of
Quartz, but more recently it has been shown that much
Chalcedony is actually a mixture of Quartz and Moganite,
another silica mineral.
includes many subvarieties such as the many varieties
of Agate, Binghamite,
Bloodstone, Carnelian, Chrysoprase, Onyx, Pietersite,
Wood, Sard and Sardonyx. When Chalcedony is concentrically
banded (often in rather wild patterns) it is called
by the subvariety name Agate. When it is in flat layers
or bands of black and white, it is called by the subvariety name Onyx.
When it is in flat layers
or bands of light and dark shades of reds, browns and
white, it is called by the subvariety name Sardonyx.
Many non-banded forms of Chalcedony - such
as Moss Agate, are
often erroneously called 'Agates'. True Agate is concentrically banded. Mottled
and included chalcedonies are more properly called simply 'Chalcedony.' Petrified
wood) is the name given to fossil wood where the replacement of the wood is by
Chalcedony, but the banding in this case is due to the wood structure - not
concentric deposition of the Chalcedony - and the material is Chalcedony, not
available from many sources worldwide.