Onyx Mineralogically is a variety of chalcedony, or quartz in microcrystalline compact masses, of opaque or semi-opaque color, uniform, covering the red-brown tones and the whole range of grays up to black.
Travertine
Travertine is a calcareous sedimentary rock of chemical type, widely used in construction, in particular in Rome, since the first millennium a.C..
