Precious opal shows a variable interplay of colors as it has an internal structure. Under a microscope you can see precious opal is composed of silica spheres some 150 to 300 nm in diameter in a hexagonal or cubic close-packed lattice. These ordered silica spheres produce the internal colors by causing the defraction of light passing through the microstructure of the opal. It is the regularity and size of these spheres that determines the quality of precious opal. Where the distance between the regularly packed planes of spheres is approximately half the wavelength of a component of visible light, the light of that wavelength may be subject to diffraction from the grating created by the stacked planes. The spacing between the planes and the orientation of planes with respect to the incident light determines the colors observed. The process can be described by Bragg's Law of diffraction. Our Products: - Opal Bracelets - Opal Earrings - Opal Pendants - Opal Rings - Loose Opals - Opal Specimens - Matrix Pendants - Bronze - Opal Fashion - Collectors Pieces - Rough Opal - Opal Books