Onyx

Onyx is a banded variety of chalcedony, a cryptocrystalline form of quartz. The colours of its bands are white and black. It is usually cut as a cabochon, or into beads, and is also used for intaglios and cameos. Some onyx is natural but much is produced by the staining of agate.

Technical Details

Chemical Composition and Name SiO₂ - Silicon dioxide

Hardness (Mohs Scale) 7

Specific Gravity* 2.65 - 2.66

Refractive index (R.I.) 1.543 - 1.552 to 1.545 - 1.554

Birefringence 0.009

Optic Sign Positive

Optical Character Uniaxial

For information about Specific Gravity, see Density

''See also: List of minerals.

Chemical Composition and Name	SiO₂ - Silicon dioxide
Hardness (Mohs Scale)	7
Specific Gravity*	2.65 - 2.66
Refractive index (R.I.)	1.543 - 1.552 to 1.545 - 1.554
Birefringence	0.009
Optic Sign	Positive
Optical Character	Uniaxial