Amber is not a birthstone, but it has been astrologically linked with the zodiac sign Taurus. Those who believe in the energies and special properties of certain stones believe that amber can improve eyesight by gazing into it, and that it cleanses the air when burned.
Amber isn't actually a stone, which is most likely why it was never assigned as a birthstone. True amber comes from ancient trees. The resin that dripped down the tree, and caught any debris in its path, including insects, is what amber comes from. It is a yellowish-brown, and when it dries, it is solid and gem-like, which is why people classify it as a gemstone. Despite its origin, amber is still used to make jewelry and other trinkets.