Opals are recognized as one of October's birthstones alongside tourmaline. Unlike standard birthstones, opals are technically not minerals. Instead, they are categorized as mineraloids because their silicon and oxygen atoms do not form a regular, repeating crystal lattice.
What Scientists Found
Opals consist mostly of hydrated silica. They form over time as water travels through rock crevices, dissolving small amounts of silica and precipitating tiny spherical particles. When these silica balls settle into orderly, tightly packed layers, they interact with light. Certain wavelengths cancel out while others reinforce each other, causing the stone to reflect different colors depending on the viewing angle. This optical effect is similar to how microscopic structures in blue feathers reflect light without using blue pigments.
The Discovery
The geological process behind opals has also preserved evidence of prehistoric life through opalized fossils. In Australia, silica dissolved in water filled voids within buried remains or replaced the original fossilized material while keeping its shape intact, essentially converting dinosaur bones into gemstones. Specific fossil ages and dinosaur species are not specified in the source; please check the official notice.
Why It Matters
Throughout ancient world history and folklore, opals accumulated a complex reputation. Ancient Romans valued them highly, but in later eras, the gem became linked to bad luck and death. This superstition was reinforced by Sir Walter Scott's 1829 novel, Anne of Geierstein, which depicted an opal with supernatural traits. Additionally, an ancient Bedouin legend held that opals fell from the sky during thunderstorms, trapping flashes of lightning within the stones.
Source: dinosaur fossil discovery - BingNews · Published October 01, 2026