_ Todays birthstone for August, peridot, was also a favorite of the ancients. This lovely transparent yellowish green to deep chartreuse stone was quite a powerful gem. It was considered an aid to friendship and was also believed to free the mind of envious thoughts. Because of the yellowish green color, it was also believed to cure or prevent diseases of the liver and dropsy. And, if that were not enough, if peridot was worn on the left arm it would protect the wearer from the evil eye. It is also popular today, but probably more for its depth of green color than its professed powers. While not particularly brilliant, the richness of its color is exceptional. Peridot comes in shades of yellowish green to darker, purer green colors. Peridot is widely available in small sizes but larger sizes are becoming scarce, so prices for larger sizes are now fairly high for good quality material. Some caution should also be exercised when wearing peridot. It is not a very hard stone and may scratch easily. Some stones may look like peridot, green sapphire and green tourmaline, and may be mistaken for peridot or be misrepresented.
Onyx is a banded variety of chalcedony. The colors of its bands range from white to almost every color (save some shades, such as purple or blue). Commonly, specimens of onyx contain bands of black and/or white.
Sardonyx is a variant of Onyx in which the colored bands are sard (shades of red) rather than black. Sardonyx is a stone of strength and protection. Use it to enhance willpower, integrity, stamina and vigor. It is believed to bring lasting happiness and stability to marriage and partnerships. It attracts friends and good fortune. Some people use sardonyx as a protection grid - placing it at each corner of the house, at doors and windows to prevent crime and misfortune.
Use of sardonyx appears in the art of Minoan Crete, notably from the archaeological recoveries at Knossos.