Sardonyx

A variety of Agate with parallel bands of white (or black) contrasting with the brownish-red body colour. Layered sardonyx stones are an ideal medium for the art of cameo, intaglio and relief carving.
General Information
A variety or type of:Agate, which is a variety of Chalcedony, which is a variety of Quartz
Chemical Formula
SiO
 
2
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Photos of natural/un-cut material from mindat.org
Physical Properties of Sardonyx
Mohs Hardness6.5 to 7
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Specific Gravity2.55 to 2.70
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Optical Properties of Sardonyx
Refractive Index1.530 to 1.543
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Optical CharacterUniaxial/+
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Birefringence0.008 to 0.010
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Colour
Colour (General)Straight white band of onyx with brownish red band of sard
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
TransparencyTranslucent,Opaque
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
LustreWaxy
gemdat.org, Management Team (2012)
Crystallography of Sardonyx
Crystal SystemTrigonal
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
HabitFibrous to grained aggregate
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Further Information
Mineral information:Sardonyx information at mindat.org
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