Onyx and Agate are the same stones, in fact. They both are, actually, just the varieties of chalcedonic Quartz. However, the Onyx and the Sardonyx have its different bands arranged in parallel layers.
The name “Onyx,” as supposed to be, derived from the Greek word signifying a nail (finger-nail), referring to its luster, similar to the luster of human nail. Sardonyx derived its name thanks to brownish-red colored layer of cornelian, also called “sard.” Sard, in turn, has got its name from Greek “Sardis,” that means “flesh,” on account of its color.
Onyx crystals were first supplied from India. Onyx has been in demand in ancient time, because it was used to create cameos and for carvings in relief on luxury vessels.
Pliny frequently mentioned Onyx in his treatises. For instance, he described 30 columns of immense size made of Onyx, set in the banquet-hall of Callistus. He also described, that the Indian fakirs worn rosaries made of onyx beads in his time. It’s reported about 2000 cups, made of Onyx, which were in the possession of Mithridates.
Numerous engraved onyxes, dated 400-300 BC, have been found during the excavation of temples and tombs on Cyprus.
It is considered in the Middle Ages, that Sardonyx is able to cure epilepsy. However, the ancients have distinguished Sardonyx and Onyx. Onyx, in turn, have symbolized a happiness in marriage. It is believed, that Onyx can bestow its wearer of oratory. Also stated, that Onyx, should wear about the neck as a mascot, thus, it will excite the passions, and stir up strife.
Onyx is mined in India, Yemen (Asia Minor), Russia, Germany (Oberstein and Idar), Ireland and South America.
Onyx is considered the Birthstone appropriate for July, according to the ancient traditions. Sardonyx, in turn, is a Birthstone for August, according to U.S. Birthstone Chart, dated 1912, and modern U.K. Birthstone Chart.
Onyx Image Credit to: Bence Fördős