The historian Josephus proclaimed a connection between the twelve stones in Aaron’s breastplate, the twelve months of the year and the twelve signs of the zodiac. The Breastplate of Aaron, referred to in Exodus 28:17-20:
10 Then they mounted four rows of precious stones on it. In the first row there was a ruby, a topaz and a beryl;
11 in the second row a turquoise, a sapphire and an emerald;
12 in the third row a jacinth, an agate and an amethyst;
13 in the fourth row a chrysolite, an onyx and a jasper. They were mounted in gold filigree settings.
14 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.
The precise list of birthstones however can be found in Revelation 21:19-20 where the foundation stones of the new Jerusalem are listed, in the order of the Roman calendar:[citation needed]
14 And the wall of the city had twelve foundations, and in them the names of the twelve apostles of the Lamb. . .
19 And the foundations of the wall of the city were garnished with all manner of precious stones. The first foundation was jasper; the second, sapphire; the third, a chalcedony; the fourth, an emerald;
20 The fifth, sardonyx; the sixth, sardius; the seventh, chrysolyte; the eighth, beryl; the ninth, a topaz; the tenth, a chrysoprasus; the eleventh, a jacinth; the twelfth, an amethyst.
The custom of actually wearing birthstones first gained popularity in Poland in the fifteenth century. Tradition suggested everyone wear the birthstone for each month, since the powers of the gemstone were heightened during its month. For the fullest effect, individuals needed to own an entire set of twelve gemstones and rotate them monthly.
