Characteristics of Onyx:

Chemical Name: Silicon dioxide

Formula: SiO2

Colors: White color-banded

Structure: Trigonal

Hardness: 7

Specific Gravity: 2.65

Refractive Index: 1.54-1.55

Lustre: Vitreous

Streak: White

Locations: India, South America, Sri Lanka, Brazil, Uruguay

What is Onyx? 

Onyx is a striped, semi-precious variety of chalcedony quartz with alternating bands of black and white. Its varieties include carnelian Onyx, which has white and red bands, and sardonyx, with white and brown bands; the name Onyx is only properly applied to the black and white variety, but is also informally used for all varieties. Onyx is a popular material for cameos and intaglios because its layers can be cut to create a color contrast. A quantity of the modern Onyx on the market is produced artificially by dying place, layered chalcedony.