Onyx, sard, and sardonyx are varieties from the micro-crystalline quartz, chalcedony. Onyx is comparable to agate, however it has straight instead of curved bands. These might be brown and black or white and white. Sard is really a brownish red variety, also much like agate.
Sardonyx, a mixture of sard and onyx, has got the straight white bands of onyx and also the brownish red of sard. The 3 varieties are carved as small sculptures and intaglios, or might be polished, tumbled or cut as beads. They're renowned as excellent materials for inlay work. Since ancient Egyptian times, onyx may be made by soaking agate inside a sugar solution, then heating it in sulphuric acid to carbonize the sugar particles. Sard might be imitated by saturating chalcedony by having an iron solution.
Found worldwide, they're formed through the decomposition of silica in gas cavities in lavas, which results within the distinctive bands.
Onyx seals were very well-liked by the Romans, who carved the pattern from the seal in negative relief to provide an elevated print. They frequently used stones with several layers, all of another colour, that have been then individually carved to make a different pattern in each layer.
Vist onyx meaning and sardonyx meaning for more information.
Onyx, Sard and Sardonyx Chalcedony
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