Onyx
(on'-iks')
12th c; gr. onux
Chalcedony with alternating black and white bands, used as a gemstone especially in making cameos and intaglios
Color
Opaque black with white bands
Family
Chalcedony - Cryptocristalline quartz
Chemical composition
SiO2
Hardness (Mohs scale)
6,5 - 7
Specific gravity
2,60 ±0,05
Refractive index
1,537 ±0,02
Optical character
None (aggregate)