The Historical Gem (back to the age of Egyptians)
The formula for Onyx is SiO2 or silica/ silicon dioxide.
Formula Mass, Color, Crystal System, ect.
Formula Mass - 60 g / mol
Color - Various
Crystal System - Trigonal
Fracture - Uneven, Conchodial
Luster - Vitreous, Silky
True Onyx or Arabic Onyx is coloured black (bottom layer) and white (top layer) while pure black Onyx is called Chalcedony
Where is it found?
Onyx is found in Argentina, Australia, Brazil, Canada, China, Czech Republic, Germany, India, Madagascar, the UK, and various states in the U.S. It is formed in the vesicles of lava.
It is mostly used for hard carving and jewelry, which is normally cut as a cabochon or beads. It is also used for intaglio and hardstone cameo engraved gems. Onyx was used to make bowls in Egypt as early as the Second Dynasty. Also slabs of onyx were used to make a shimmering semi-translucent interior wall.