What is Sardonyx?


Sardonyx is a variant of onyx, which is itself a variety of chalcedony. Sardonyx is characterized by its layers of sard and onyx, showing contrasting bands of colors like red, white, and brown. It’s primarily found in India, Brazil, and Uruguay.

Sardonyx is a unique gemstone that comes in layers of contrasting colors, often including red, white, and brown. Its banded appearance makes it a popular choice for cameos, beads, and other ornamental uses.

Gemstone Properties

Chemical ClassificationInorganic - Silicate (Chalcedony)
ColorSardonyx displays alternating bands of reddish-brown sard and black, white, or clear onyx.
LusterWaxy to vitreous.
OccurrenceIndia, Brazil, and Uruguay.
FormationSardonyx forms in hydrothermal veins and in cavities in volcanic rocks.
DiaphaneityTranslucent to opaque
Mohs Hardness6.5 to 7.
Specific Gravity2.58-2.64.
Diagnostic PropertiesBanded red and white chalcedony.
Chemical CompositionSiO2
Crystal SystemHexagonal (variety of Quartz)
Optical PropertiesUniaxial (+)
Refractive Index1.530 - 1.539
2V angleNot applicable (isometric)
DispersionNot notably high.