Birth stones can vary but most are constant and there has been a generally accepted standard for many years. One major anomaly is for June which traditionally was the Pearl but has more recently been replaced by Alexandrite.
Obviously it might be a good idea to select a stone which represents a birthday but equally you may select a stone because you like it. With 6mm diameter Cubic Zirconia stones set in 925 sterling silver these studs look stunning with the and look and feel of the real thing.
Perhaps you will simply choose a set of earrings which appeal to you but if you are looking for a particular birth stone the table below is a guide.