It is a form of Quartz whose natural crystals are too small to see
without high magnification.
In common
practice, only the translucent, single colour types of quartz
are
called "chalcedony".
Most popular members
of this variety are; Aventurine
-soft blue-green
with inclusions of mica which shimmers.
Blue Chalcedony -mid-blue
which often varies in colour, because it can
have an overtone of grey or pink, the latter giving it a lavender hue.
A heavenly gemstone which often shows a moonlight shimmer - Black Onyx
naturally occurs in nature in thin bands. Most Black Onyx sold in shops
is dyed.
Carnelian
ranges in colour from
yellow-orange to reddish-orange, to orangey-brown, and can vary from
semi-opaque to highly translucent.
Chrysocolla Chalcedony
is a
rare gemstone is often called Gem Silica,
is blue to turquoise in colour.
Chrysoprase
is highly prized in
its best colour-apple-green, but it can
be olive-green, pale green and whitish.
Its density ranges from almost opaque to translucent.
By Jeff-o-matic via Flickr.com
Jasper is an
exception in the
Chalcedony group because it is opaque.
Colour range is solid brownish-orange, yellow-beige, muted green and
greyish.
Tiger Eye
occurs in brown
yellow, pink, and red with a silky lustre,
seems to have received its name from its bands resembling the eye of a
tiger.
This site uses British
English, which is the English we use in
Australia.
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