I saw this on the web while I was researching birthstones :
Where did birthstones come from?
Some people think that came from came from the Bible. Others think that the birthstones are tied to the wisdom of ancient Atlantis, where history and myth tell us an advanced race of humans was able to do many things, including flight and astrology. Finally, some believe that the birthstones were found by the original druidic and pagan religions, where it was learned that all stones have a certain vibration that their chemical composition reacts to and that this vibration resonates with the natural vibrations of people born during each month. Okay I'm not so sure about the people of Atlantis, but this is what I've been able to come up with.

Early civilizations in both India and Babylon as far back as 3000 BC invested rare and beautiful gemstones with magical properties. Quite often before a person talked to a Jeweler they consulted with some sort of astrologer first. The Indian and Babylonia system both linked the ruling planets with their corresponding gems. Giving rise to the zodiac type system that we use today.

The early gem buyers sought advice from astrologers first, in hopes that they could influence the forces that were identified with the planets in their favor. Because there was no formal classification of gemstones, a gem was assigned each sign of the zodiac based on a color system. Color was thought to unleash the power attributed to the stone.

The astrological concept of gems worked its way into Judo-Christian tradition through the 12-gem breastplate of Aaron as recorded in the Bible, in Exodus 28 and 39. Most scholars considerer this to be the origins of our modern birthstone list. The following describes the High Priest's breastplate:

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"It was square -- a span [22 centimeters] long and a span wide -- and folded double. Then they mounted four rows of precious stones on it. In the first row there was a ruby , a topaz and a beryl; in the second row a turquoise, a sapphire and an emerald; in the third row a jacinth, an agate and an amethyst; in the fourth row a chrysolite, an onyx and a jasper. They were mounted in gold filigree settings. There were twelve stones, one for each of the names of the sons of Israel, each engraved like a seal with the name of one of the twelve tribes." (Old Testament, New International Version, Exodus, Chpt. 39, vs. 9-14)

NOTE: No matter whose translation of the word or scripture you read - Protestant, Catholic, Greek, Hebrew, Egyptian, Babylonian or Assyrian - you will note the placement of stones in the breastplate differ - as do the names of each. This was because there were no specific names given to gemstones as there are today. Many were named regionally. Some carried the name of the city or country of origin such as Chalcedony (Turkey). They did not analyze these favored stones by their composition or crystalline form in those days. In addition, to confuse things even more, New Advent tells us their 'chrysolite is our topaz and sapphire is our lazuli'.

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Theologians debated the importance of these gems, and what they really were. In the late 15th century scientist, begin to launch an attack on the idea that gems held any mystical importance. By the 1600's, zodiac gems were losing the race to birthstone gems.

The American National Association of Jewelers made the modern birthstone list public in 1912. The list was a source of some controversy; many of the gems were moved or dropped from the list completely. Some gemstone purist felt that this was a crass commercialization of the Zodiac / Birthstone list.

Since I have been in the business I have seem Citrine replace Topaz as Novembers birthstone. And there is now (2003) a big push to make Tanzanite Decembers new Birthstone.