Birthstones are gemstones that represent the months in a year. There are several variations of birthstones, such as Jewish birthstones (some people structured the stones based on the gemstones on Aaron's breastplate), and modern birthstones that are widely popular/ commonly acceptable. The modern birthstone list was created in 1912 by the organization Jewelers of America, in an attempt to standardize birthstones. Here is the list of modern birthstones based on Gregorian calendar.