Article content The idea of associating precious stones with months of the year was a marketing gem. Most historians trace the concept to the Book of Exodus. Aaron, the high priest, wore an ornate garment emblazoned with stones, one for each of the 12 tribes (28:17-20). We apologize, but this video has failed to load. Try refreshing your browser. Most of those stones are among the birthstones of today. Later, the gems were linked with the 12 signs of the zodiac. The wealthy wore a different one each month. Then, in 18th century Poland, traders began marketing specific gems as birthstones. In ...