There are several possible birthstone choices for the month of August: peridot, carnelian, sardonyx, diamond, or sapphire - the choice depends on which "birthstone list" you are reading! Personally, I really like all of the possible choices, so let me tell you a little bit about each one, then you can decide which you like the best.
Peridot is an ancient gemstone with a rich bright yellow green color. It's a fairly hard stone. Peridot is thought to attract love and to soothe the nerves.
Carnelian is another ancient stone - known and used since Biblical times. Carnelian is a form of chalcedony. The red color comes from iron impurities. Carnelian is thought to increase energy and to protect the wearer from evil.
Sardonyx is a banded stone known from ancient times and occuring in either red/white or black/white.
Sapphire - Blue sapphire is the most popular color, but sapphires occur in a wide range of colors from colorless to pink, also purple , yellow, orange, brown, and even green.
Diamond is the hardest of known stones and the rarest. diamonds are available in a wide assortment of colors and colored diamonds are very popular right now. Diamond is thought to encourage hope and to promote healing.