One of the earliest writers to associate with the apostles the symbolism of the gems given in Revelations is by Andreas, bishop of Caesurae. He gives a brief description of the stones, which is recounted in George F. Kunz's book The Curious Lore of Precious Stones (1913).
* The Sardonyx, represents James. Sardonyx or Onyx: Hebrew name of Yahalom. The traditional interpretation is onyx. Some Greek writers considered it to mean diamond as the translation of the Hebrew word means to smite or cut. However, there is no evidence that the Hebrews knew of diamond. However, onyx was a well-known stone, which was carved into seals and used with wax. Therefore, the term to smite may mean to strike as with a seal on hot wax. Onyx is a common soft stone, composed of calcium carbonate and deposited in caves. Much banded onyx (sardonyx) today is cut and polished as inexpensive novelty items. *
Sardonyx - A semi-precious stone that is formed by two layers, a red-brown layer of sard and a gray, white, black or brown layer of onyx. Sardonyx is a type of quartz (agate), it is frequently carved to make intricate cameos and seals.
Agate - Hebrew name of Shebo. A banded variety of agate, commonly used by Egyptians, had distinctive gray and white alternating bands that would have contrasted well with the other varieties of fine-grained quartz.
Sardonyx was highly valued in Rome, especially for seals, because it was said to never stick to the wax. Roman General Publius Cornelius Scipio was known for wearing lots of sardonyx.
Folklore says sardonyx helps promote healthy relationships, and helps to balance heaven and earth.