How does opal get its color

Most of us know how a gem gets it color. Maybe because of the crystalline structure, or there is some composition for instance copper, iron, aluminum or the impurity in it may cause its color. Actually, the play of colors in opals need count on the diffraction. Scientists discovered with electron microscope precious opals are made up of tiny uniform spheres of transparent hard silica. They fit together in an orderly three dimensional frame. When light passes through the transparent spheres in a direct line, at the moment it encounter with the silica, it will be bent and deviate into different angles, so the opal gets rainbow effect.
So what factor affects the deflection and diffraction? Various colors been diffracted through different size of spheres. That’s simple the bending of deflection and breaking up of diffraction, this two main factor make the rays create all kinds of colors. You can make a test by moving the stone, light shoots the spheres from different angles and cause the change of colors. It’s said that the name of opal, in fact meaning “to get changes in color”. Based on the internal mechanism experts had divided opals into many different categories; there are white opal, fire opal, and black opal. On market, the black opal is rarer. Still any color of opal is quite popular; you can easily find various colors of them appear on rings, pins, or earrings.