Iridescence
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Iridescence is the phenomenon of certain surfaces that appear gradually to change colour as the angle of view or the angle of illumination changes. Iridescence is caused by wave interference of light
Iridescence in soap bubbles
Fuel on top of water creates a thin film, which interferes with the light, producing different colours. The different bands represent different thicknesses in the film. This phenomenon is known as thin-film interference.
An iridescent biofilm on the surface of a fish tank diffracts the reflected light, displaying the entire spectrum of colours. Red is seen from longer angles of incidence than blue.
The pearlescent shell of a black-lip pearl oyster
Opal
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Opal is a hydrated amorphous form of silica; its water content may range from 3% to 21% by weight, but is usually between 6% and 10%. Due to the amorphous physical structure, it is classified as a min
Iridescence
…light in microstructures or thin films. Examples of iridescence include soap bubbles, feathers, butterfly wings and seashell nacre, and minerals such as opal. Pearlescence is a related effect where some or most of the reflected light is white. The term pearlescent is used to describe certain paint finishes…
A rich seam of iridescent opal encased in matrix
Precious opal consists of a regular arrangement of silica nanospheres in closely packed planes (idealized diagram).
This precious rough opal from Coober Pedy, South Australia, displays nearly every color of the visible spectrum.
Common rough opal