Sardonyx Gemstone Beads

Frequently asked questions

• What is sardonyx made of?

  Sardonyx is banded chalcedony — a microcrystalline quartz at Mohs 6.5–7 — composed of alternating layers of sard (brownish-red to orange chalcedony) and onyx (white or black chalcedony). The classical historical form is reddish-brown sard bands alternating with white onyx bands, used in Roman cameos and signet rings. The modern bead trade more commonly carries black-and-white banded sardonyx, often produced through dyeing or heat treatment of chalcedony rough.
• Is sardonyx natural or dyed?

  Both natural and treated sardonyx exist in the bead market, and treated material is common. Dakota's current active catalog tags 8 of 16 strands as dyed and 4 as heated; treatment is part of how most modern commercial sardonyx achieves its color register. Bright saturated colors — vivid purple, electric blue — are dye signals; sardonyx does not naturally occur in these colors. Black-and-white banded sardonyx may be heated, dyed, or in some cases minimally treated depending on the source rough. Treatment should be disclosed — ask before buying if a strand doesn't specify.
• What's the difference between sardonyx, sard, and onyx?

  Sard is solid brownish-red to orange chalcedony with no banding. Onyx is banded chalcedony, typically black-and-white. Sardonyx is the banded combination — historically reddish-brown sard alternating with white onyx, today most commonly black-with-white in the bead trade. All three share the same chalcedony chemistry, the same Mohs 6.5–7 durability, and the same care profile; the difference is visual register.
• How is sardonyx different from agate?

  Both are banded chalcedony. The visual distinction is band geometry: sardonyx shows straight, parallel, often thin and even banding, while agate's banding is typically wavy, concentric, or irregular. Sardonyx's straight parallel banding is what made it the preferred stone for Roman cameo carving — the layers cut cleanly for relief work. Mineralogically, both are microcrystalline quartz at Mohs 6.5–7; the buying decision is band pattern and color register.
• How durable is sardonyx for daily wear?

  Mohs 6.5–7 — durable enough for any jewelry application, including rings, bracelets, and necklaces. Standard care is a soft cloth with mild soap. Because most commercial sardonyx is dyed or heated, avoid prolonged ultrasonic or steam cleaning (extended exposure can affect dye stability) and keep away from aggressive household cleaners. Color stability is good under normal wear conditions.