What is Onyx?


Onyx is a variety of chalcedony, which is itself a form of quartz. It’s characterized by its parallel banded layers, which can be black, white, or a combination of both. Onyx is primarily found in various regions including Brazil, India, and Madagascar. It has been used for centuries for both decorative and functional purposes, including in jewelry and carving.

Onyx is a banded variety of chalcedony characterized by parallel layers of black and white. Its striking appearance makes it a popular choice for jewelry and decorative items. The stone has a long history of use, dating back to ancient civilizations.

Gemstone Properties

Chemical ClassificationInorganic - Silicate (Chalcedony)
ColorTypically black, but can also be white or banded black and white.
LusterWaxy to vitreous.
OccurrenceBrazil, India, Madagascar.
FormationOnyx is formed in the gas cavities of lava.
DiaphaneityTranslucent to opaque
Mohs Hardness6.5 to 7.
Specific GravityApproximately 2.55 to 2.70.
Diagnostic PropertiesBanded chalcedony, often black and white.
Chemical CompositionSiO2
PleochroismNot exhibited in onyx.
Crystal SystemHexagonal (variety of Quartz)
Optical PropertiesUniaxial (+)
Refractive Index1.530 - 1.539
2V angleNot applicable (isometric)
DispersionNot typically relevant for onyx.