Onyx

Onyx is a banded calcite formed in caves by mineral-rich water. It is translucent, dramatically patterned, and soft — the three facts that determine every correct use of it.

Where it performs

• Backlit feature walls, bar fronts and reception desks
• Vanity tops in high-end residential and suites
• Fireplace surrounds and niche panels
• FF&E — table tops, insets, decorative panels

Backlighting is what onyx is for. Lit from behind, the banding reads as depth and the material stops looking like stone and starts looking like glass. It is the single most effective use of a small budget of expensive material.

What to watch

• Soft and brittle. Most slabs are mesh-backed at the quarry, and many need reinforcement during fabrication. Involve the fabricator early.
• Not suitable for kitchen countertops, flooring or anything exterior.
• Slabs are typically smaller than granite or marble. Plan layouts around real slab sizes, not nominal ones.
• Onyx etches readily. It is calcite.

Selecting

Onyx must be seen. Photography flattens translucency, and a lit sample looks nothing like the same slab unlit. For a backlit application, view the actual slab on a light table before committing.

Finishes

Polished, almost universally — it is what brings out the translucency. Honed is occasionally used where a softer read is wanted.