Onyx

A solid black Chalecedony.  Onyx is often confused with marbles, yet it is a significantly different rock type. Onyx is a sedimentary rock, formed as stalactites and stalagmites in cave interiors. This formation method results in the cryptocrystalline construction of the rock fabric, and it is the size and uniformity of these crystals that contribute to the classic translucent property of most onyx varieties. While vulnerable to chemical and abrasive attack, the decorative appeal of onyx is perhaps unsurpassed by any other material. 

Chemical composition

Si02

Color Black, white or banded
Lustre Vitreous, silky or dull
Hardness 7
Crystal system trigonal
Origin India, Brazil
Healing properties*

Onyx helps to ground and concentrates energy while helping us to cleanse and purify. Quietens powerful emotional states. Encourages stillness and introspection.
Folklore

Onyx takes its name from the Greek word "onyx", which means fingernail; this could be due to a Greek legend, in which Eros mischievously cut the fingernails of Aphrodite with an arrowhead whilst she slept, and the gods turned the clippings into stone. Onyx was cut and carved as a gemstone by the Ancient Greeks and Romans in cameos. Intaglio etchings (negative relief engravings) were also made from onyx. These carvings showcase the banding of onyx.