Onyx,
in Los Angeles.

Onyx is a chemical sedimentary stone — bands of calcite laid down by groundwater over thousands of years. The bedding is what makes the slab: vein-cut runs the bands as long horizontal strata, cross-cut takes the cut perpendicular for concentric cloud-like pools, and wave-cut sits between the two with sweeping diagonals.

The defining property is translucency. Every onyx slab worth specifying should be walked with a flashlight to the back, or lit from behind in the yard — the read of the stone changes completely when light passes through it. Bars, fireplace surrounds, vanity panels, and powder bath walls are the canonical applications, almost always backlit with a discreet LED panel.

Onyx is structurally softer than marble and well below quartzite. It belongs on vertical surfaces and decorative horizontals — not on a daily-use kitchen island. Most slabs are sold resin-stabilised (Antolini AVP and equivalents); ask before specifying for water-exposed applications.