October has 2 birthstones, one of them is Opal. Each Opal is truly one of a kind. 

Each stone flickers with a unique fire and a good opal is one with an opinion of its own.

Jewels, A Secret History - Victoria Finlay

Some prefer the calming flashes of blues and greens; others love the bright reds and yellows. With its rainbow of colors, as you turn and move the Opal the color plays and shifts, giving you a gem that can be worn with a plethora of ensembles.
The ideal Opal is one that displays broad patterns covering the surface, with all the colors of the rainbow. Opals are the most individual gemstone with its range of colors.
The play of color you see in Opal is due to millions of tiny silica Spheres of different sizes. These spheres refract light and cause the beautiful spectral colors visible in opal. The spheres have to be just the right size and of a uniform nature to create enough color for our eyes to see.

History and Origins

In ancient times, the Opal was known as the Queen of Gems because it encompassed the colors of all other gems. Opallios is the Greek word for Opals meaning to see a change of color. The Roman word for Opal is Opalus meaning precious stone. The ancient Greeks believed that opals were formed from the tears of joy wept by Zeus when he defeated the titans, and that the opal bestowed prophetic powers.

Opals of all varieties have been used for everything from easing childbirth to bringing strength in battle. Long known as the Wish Stone, Opal is supposed to promote love and romance and to grant wishes and personal happiness.