Chalcedony

The term chalcedony is derived from the name of the ancient Greek town Chalkedon in Asia Minor.

Chalcedony is the form of a variety of mineral quartz that is compact and microcrystalline. It's found in many different colors as it occurs in many different shapes, sizes and forms and many varieties of it have been used as gemstones since antiquity. The term Chalcedony is often used specifically to describe the white, gray, or blue translucent type of Chalcedony. .its hardness according to the Mohs scale is 6-7.

Chalcedony is found worldwide. It's known by its popular names rather than this name, which refers to the brand group of microcrystalline quartz

Agate:

It's the most well-known and unique form of Chalcedony. Agate doesn’t describe a specific mineral but it's a group of forms for microcrystalline variety of silica. Its multicolored banded one.

 

Aventurine:

It has for the most a green color, containing small Mica, Hematite; it's an opaque with a compact form.

Bloodstone:

It's one of the oldest known gemstones that belong to the quartz family. It's Dark green to greenish blue variety with red or brown spots.

Carnelian:

It's Red to amber-red translucent variety. Some forms of it are heat treated to darken it.

Chrysoprase:

It's one of the more popular gemstone forms of Chalcedony. It has a green color.
Jasper:

They are brown, reddish or yellow Chalcedony; often multicolored and spotted
with Opaque form.

Onyx:

It May refer to either solid black Chalcedony, or a form used for engraving that has a black base and white banding or a white upper layer. Onyx is the most traditional black gemstone.

Sard:

It's Brownish to brownish-red, transparent to translucent form.

Tiger's Eye:

It’s a compact Quartz. Tiger's Eye is famous for its chatoyant effect as it has also a glistening sheen.