Fireworks. Jellyfish. Galaxies. Lightning. Opal's shifting play of kaleidoscopic colors is unlike any other gem.
Opal's microscopic arrays of stacked silica spheres diffract light into a blaze of flashing colors. An opal's color range and pattern help determine its value.
Grids of silica spheres 0.2 microns in size create red play-of-color flashes.
The novel "Anne of Geierstein" gave opal a reputation of being unlucky.
Opal contains up to 20% water trapped in its silica structure.