Assertion: opal's color | /r/HasProperty | optical effects
Facets:
Source sentences:
text: The color is not due to any pigment in the stone, but are optical effects created when the microscopic spheres of silica hardened in an orderly grid-like pattern, similar to layers of ping-pong balls in a box.
text: The color is not due to any pigment in the stone, but are optical effects created when the microscopic spheres of silica hardened in an orderly grid-like pattern, similar to layers of ping-pong balls in a box.