According to the American Gem Society, the origin of birthstones date back to the breastplate of Aaron -who were the brother of Moses- which contained twelve gemstones representing the twelve tribes of Israel.
A birthstone is associated with each month of the year.
You can refer to the picture below to identify yours. 
As an authorized Lali Jewels dealer. World Wide Weil carries a full range of birthstones jewelry, including pendants, earrings and rings in both 14k and 18k Gold.
The pendants and earrings are available in oval and round.