A long time ago Jewish historian Josephus made a connection between twelve gemstones from the breastplate of Aaron with twelve months of the year and all twelve Zodiac signs.
According to him, gemstones on its breastplate signify tribes of Israel described in the Book of Exodus. You can buy moonstone birthstone online whenever required.
Although interpretations the of Book of Exodus describing breastplate gemstones are not accurate, Josephus provided two lists for those stones.
During the eighth and ninth-century religious people associated mentioned gemstones with apostles. Back then it was the practice to wear one gemstone every month. The tradition of wearing just one gemstone as a birthstone is just a few centuries old.
Historians argue even today about this tradition stating that this custom started in Poland or Germany. Traditional birthstones are society-based and contain many gemstones that were the most common choice reflecting Polish traditions.
National Association of Jewelers standardized birthstones in 1912. They adopted a list of birthstones that was updated in 1952 by the Jewelry Council.
The list of modern birthstones changes few more times in recent history by adding Tanzanite as December birthstone in 2002 and Spinel as August birthstone in 2016.
British created their own standardized list of birthstones in 1937 by Britain's National Association of Goldsmiths.
Before the creation of standardized lists of birthstones, there were no strict rules. Most of the classifications were focused on the gemstone color rather than the exact stone variety.
Because of that, we can find that Ruby and Garnet were used as of January birthstone for being the same color.
We find this even today with classification for December birthstones where Turquoise, Blue Topaz, and Tanzanite have the same blue color.