Opal
Birthstone for October
Opal is unlike any other gemstone. Its internal structure — a grid of microscopic silica spheres — diffracts light into flashing spectral colors that shift as the stone moves. This phenomenon, called 'play of color,' can include every hue in the visible spectrum, and no two opals display the same pattern. Australia produces over 90% of the world's gem-quality opals, with the town of Coober Pedy nicknamed the 'opal capital of the world.' Black opals — with a dark body color that makes the play of color more vivid — are the most valuable variety. Opal is relatively soft and contains water within its structure, which makes it sensitive to heat and dryness.
Why Opal for October?
Opal became October's stone because its shifting colors were seen as a reflection of autumn's changing leaves. In the Middle Ages, opal was called 'opallios' — a combination of all gems — and October, as the month when the year begins to turn, was associated with transformation and the play of light and dark.