ONYX
Onyx is variety of the microcrystalline quartz, chalcedony. It's similar to agate, but it has straight rather than curved bands. Onyx seals were very popular with the Romans, who carved the pattern of the seal in negative relief to give a raised print. They often used stones with several layers, each of a different colour, which were then individually carved to produce a different pattern in each layer.
Onyx is variety of the microcrystalline quartz, chalcedony. It's similar to agate, but it has straight rather than curved bands. Onyx seals were very popular with the Romans, who carved the pattern of the seal in negative relief to give a raised print. They often used stones with several layers, each of a different colour, which were then individually carved to produce a different pattern in each layer.