Black Onyx Tumbled 2-3cm

Naturally tumbled Black Onyx in a 2–3cm size, displaying a deep black to dark charcoal body with a high-gloss polish and subtle grey banding visible on some pieces. Each stone varies slightly in shape and surface sheen. A popular choice for crystal collections, display bowls, and monochromatic decorative styling.

Onyx is a banded variety of chalcedony (microcrystalline quartz — silicon dioxide), characterised by parallel layers of alternating colours. Black Onyx as sold commercially is typically grey-banded chalcedony that has been treated with a sugar-acid or heat process to permanently darken the stone to a uniform deep black — a practice that has been standard in the gem trade since ancient Roman times. The treatment is stable and does not affect the stone's durability. Onyx forms in the gas cavities of lava flows and is found worldwide, with significant sources in Brazil, India, and Madagascar.

Stone Details

• Mineral: Black Onyx (treated banded chalcedony — microcrystalline silicon dioxide)
• Form: Tumbled, polished
• Hardness: Mohs 6.5–7
• Size: Approximately 2–3cm per stone
• Colour: Deep black to dark charcoal with subtle grey banding on some pieces
• Finish: High-gloss polished
• Weight: Approximately 200g per lot
• Sold: Per stone — shape, size, and surface sheen will vary

Shape and surface reflectivity will vary naturally between individual stones. Subtle grey banding may be visible on some pieces, reflecting the natural layered structure of the chalcedony.