By Melissa Sherrard • Updated March 24, 2022
The Sardonyx is a semi‑precious gemstone prized for its striking banded patterns and historical significance. Its name derives from the Greek words sard (reddish‑brown) and onyx (veined gem).
Technically a variant of onyx, Sardonyx is composed of layered silica (SiO₂) crystals that form alternating bands of color. Unlike pure black onyx, Sardonyx displays a spectrum of translucent, opaque, and solid hues that result from quartz fibers stacked over time.
Known as banded agate, Sardonyx is distinguished by its repeating dark and light bands—typically white, gray, red, and brown—creating a visually striking contrast that sets it apart from its black counterpart.
In antiquity, Sardonyx was valued even above sapphire, silver, and gold. Roman soldiers wore engraved talismans of the stone, believing it could channel the power of the carved figure. During the Renaissance, orators prized the gem for its reputed ability to enhance eloquence.
Today, Sardonyx remains an August birthstone, celebrated for its aesthetic appeal and the depth of its historical lore.
