Book 27, Question 83
What makes an opal flash rainbow colors?
Opal is made of tiny silica spheres stacked in neat layers, with water in between.
When light enters, the layers bend it and split it into colors, creating flashes that change as you turn the stone. This is called play of color. Opals aren't true crystals because their pattern is not completely regular, but they shimmer. Much of the world's opal is found in Australia.
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Quick answers
What makes an opal flash rainbow colors?
Opal’s flashing play-of-color is caused by diffraction of light by silica spheres stacked like tiny Ping-Pong balls in a box.
Source: GIA
More fun facts
- Opal's spectacular play-of-color can display all the colors of the rainbow.
- Grids of silica spheres 0.2 microns in size create red play-of-color flashes.
- Opal’s arrays of silica spheres form a fantastic variety of patterns and colors.
- Fine opals are often cut into irregular shapes that keep as much play-of-color as possible.
Sources: GIA