May Birthstone

 Modern birthstone: emerald
Zodiac gemstone for Taurus: sapphire
Ancient traditional birthstones:
Hebrew: agate
Roman: agate
Arabic: emerald
Hindu: emerald
Polish: emerald
Guardian angel: Amriel
His talismanic stone: carbuncle (garnet)

History of emerald

Thousands of years ago, the ancient Egyptians mined the Earth, suffering through extreme conditions to find the prized green emerald. Cleopatra was so taken with these stones that she claimed the mines for herself. In fact, she was known for wearing lots of huge emerald jewelry, and gave emeralds carved with her portrait to her important visitors. 

Science of emerald
Emerald is another variety of beryl, the mineral that includes aquamarine (blue), heliodor (yellow to gold), and morganite (pink to peach). The reason for emerald's vivid green color is that chromium and iron infiltrated its mineral structure during formation. It is surprisingly common for emeralds to contain flaws and veins of chemicals called inclusions. These little imperfections are an accepted feature of the stone's identity.

The custom of wearing birthstones probably first became popular in Poland in the fifteenth or sixteenth century. For more information about the history of birthstones, try The Curious Lore of Precious Stones by George Frederick Kunz, a fascinating compendium of all the powers that have been associated with gemstones through the ages. For example, birthstones originally may have been worn each month by everyone, since the powers of the gemstone were heightened during its month. If that is true, to get the full effect, you need to go out and get a full set of twelve and rotate them each year!