October has two birthstones: opal and tourmaline ... The gemstone is known for its "play-of-color," or ability to shift hues. Rough opals appear white, but once polished, their surface shines ...

Opal is the traditional birthstone for October. This gemstone is well-known for its "play-of-color," or ability to shift color. Opals often have a kaleidoscope of colors on their surface.