Peridot is the principal gemstone for August, however, the original birthstone was Sardonyx. Spinel was added as the third birthstone for August which gives August babies a plethora of choices owing it to its range of colors.
Another birthstone for the month of August is the Sardonyx. It is categorized as silica mineral, chalcedony. Sardonyx is a variation of the onyx stone. It has a banded appearance because of its layered tiny quartz fibers.