Sometimes, that gel was stuck in bones or bits of wood that had already started to fossilize, so the silica trapped in there formed opals in the shape of those organic structures.
The basic idea of mining is basically extract the opal clay out from the ground, put it onto a truck, I take the truck to a puddling site in town, and check if there's opal in that.
Suddenly one of these gypsies in trembling opal, seizes a cocktail out of the air, dumps it down for courage and moving her hands like Frisco dances out alone on the canvas platform.
He paused to examine a long coil of hangman's rope and to read, smirking, the card propped on a magnificent necklace of opals, Caution: Do Not Touch. Cursed—Has Claimed the Lives of Nineteen Muggle Owners to Date.
For the sake of simplicity, let's look at what happens when a single color of light — green, with a wavelength of 500 nanometers — hits a precious opal.
The ordered structures that cause iridescence in opals are called photonic crystals, a kind of crystal where the bending and reflecting of light is happening in three dimensions in a periodic or repeated pattern.
This shimmering, dazzling, dancing display of light comes about from a confluence of chemistry, geology, and optics that define opals from their earliest moments, deep underground.