Happy Birthday October, your birthstone is the mysterious Opal!
The majority of the world opals are mined in Australia, followed by Ethiopia. Opals have also been found in the USA in the state of Nevada. In fact the largest black opal is located in the Smithsonian. It is known as the "Roebling Opal". The 2,585 carat opal was found in the Rainbow Ridge Mine, NV in 1917.
Each and every Opal is unique, each are individuals with distinct colors, shapes and sizes. Such as the Flame Opal that has streaks or bands of red that move across the surface resembling fire. Or the Harlequin /Mosaic opal with its angular play of color and broad patches, creating a highly desirable gem.
Like many gems throughout history, the opal was believed to grant good luck as it represented all the virtues with its broad spectrum of colors. It was also thought to render its holder invisible when wrapped in a bay leaf. It wasn't until the early 19th century that opals were thought to bring bad luck, due to the popularity of Sir Walter Scott's novel, Anne of Geierstein. In the book, the character Hermione wears an enchanted opal. The opal is sprinkled with holy water and the gem immediately loses its luster and just as suddenly Hermione dies in her chambers with nothing left of her but a small pile of ashes.
Opals are very delicate and only have a 5.5 rating on the Mohs scale. They are susceptible to scratches and because gem grade opals usually have a 6-10% water content, they have a low tolerance to changes in temperature and easily develop cracks or "crazing" as they dehydrate. As such, Opals aren’t recommended to be set in rings, unless the stone is placed in a protective setting or reserved for occasional wear.