Throughout history, various gems and precious stones have been attributed to each of the signs of the zodiac. There is little agreement as to the "correct" birthstones. There are ancient as well as modern assignments of stones to the signs and planets with controversy surrounding most. The use of gems as talismans was founded on the assumption that different stones possess different powers and virtues. Depending on which experts you consult, the use of gems as charms began in either ancient India or Babylon at least 4,500 years ago. In both places, the choosing of gems was far too important a duty to entrust to jewelers. One consulted an astrologer for recommendations based on one's horoscope. Later, Jewish and Christian theologians developed their own interpretations of the 12-gem breastplate of Aaron made 3,500 years ago.
The modern birthstone list came into being in 1912 in Kansas City, Mo., when the National Association of Jewelers met to revise the list which had been in widespread use since the 15th century. Gemstone purists complained that the new list was devised for commercial purposes. As a result, astrologers who prescribed gems often substituted alternate or secondary stones. Although in the West, different gems have been recommended to tally with the date and month of birth, numerology and sign of the Zodiac, in Indian Astrology several factors have to be taken into consideration along with a horoscope and the position of various planets and their influence in life before gems are advised for wear. However, the navaratna (nine gems) are suitable for almost all persons. It is believed that the nine stones when worn together bring abundant wealth, happiness, renown, longevity, honour and mental peace.