"No two opals are the same. Light refracted by silica spheres in the stone creates a kaleidoscope of color, called “play-of-color.” Sometimes fine opals are cut irregularly to highlight the range in the play-of-color. Opals have been valued throughout history — the Romans believed they were the most precious gemstones of all, and the Bedouins believed that the stones contained lightning and fell from the sky during storms."
"This shimmering stone is formed when seasonal rains soak into dry ground, carrying silica down into the earth. The silica deposits then solidify underground, creating opal. This process generally occurs in desertlike areas, particularly in Australia."