Translucent onyx
Onyx is translucent. Held against a light source, the banding inside the stone shows through the body, rather than sitting on the face, which is why it is used for backlit panels, bar fronts, feature walls and the occasional lit vanity.
That also means an onyx slab looks like two different stones depending on whether the light is in front of it or behind it. Judging one from a photograph taken in a yard tells you very little about what it will do in the application it was chosen for.
Against jewelry onyx
The black onyx of rings and cufflinks is a chalcedony, a form of quartz. The onyx sold as slabs is a different material entirely: a banded calcite stone, deposited in layers, related to travertine and marble, not to quartz.
The two share a name and nothing else, which explains why stone onyx is pale and translucent while jewelry onyx is opaque and black. Our range runs white, gray, honey, beige, green and one black, all of them stone onyx instead of the jeweller's material.
Slab thickness
All of our onyx comes at 3/4 inch, the thinnest natural stone we carry, and there are two reasons for it. Light has to get through, and the thinner the stone the more of it does, which matters on every backlit application. And onyx blocks yield less usable material than marble blocks do, so cutting thinner is how a block is made to go further.
Onyx also fractures more readily than marble does, which is why slabs are often supplied with a mesh or resin backing applied at the processing stage to hold the stone together in handling and fabrication. That backing matters for one application in particular: it sits between the light and the stone, so on a backlit panel it affects how evenly the light comes through. A clear resin backing still passes light and a mesh one shows through, so if a slab is destined to be lit, what is on the back of it is a question for the reservation rather than the delivery.
The polished finish
Eight of the nine slabs we carry are polished. A polish is what makes the depth in the stone visible: the banding sits at different levels within the body, and a reflective surface lets the eye read down into it.
A honed onyx trades some of that depth for a quieter surface, which is what a room wants when the stone is covering a large area or sitting somewhere a reflection would be distracting. It is the less common choice here simply because most onyx is bought for the depth.
Reading the banding
Onyx was deposited in layers, and those layers run through the slab as bands rather than as the branching veins a marble carries. The bands can be tight and parallel or broad and wandering, and on some stones they curve into rings where the deposit built up around a point.
That structure decides what a finished panel looks like far more than the color does. Two honey onyx slabs can be a quiet striped stone and a dramatic swirled one, and the only way to tell them apart is to look at the whole slab and not a corner of it.
Where onyx is used
It is a feature material, and it is at its best on a vertical surface or a panel where light can reach it from behind. That is the job it is made for, and it is a job nothing else in the range can do at all.
The marble page covers the chemistry onyx shares, the quartzite page covers the harder working surfaces, and the stone slab overview sets out how lots and selection work.
