It’s a kind of chalcedony. Onyx is a different stone known marble. From the outside it is very difficult to distinguish from marble, but the Onyx stone is translucent and light-brilliant, Marble is completely impermeable. When marble is obtained from near-surface layers, Onyx stones are found in much deeper layers and are valued according to their color. The most worthless onyx is the color of the siphon, the White, Gray, Brown, Yellow and Green according to the value order.