Opalisointi

Opalisointi refers to the optical phenomenon that gives opals their characteristic play of color. It is caused by the diffraction of light from a regular, repeating structure of silica spheres within the opal. These spheres are typically uniform in size and arranged in a close-packed lattice. When white light strikes this structure, it is diffracted, separating into its constituent colors, which are then seen by the observer. The size of the silica spheres determines the colors that are diffracted. Smaller spheres diffract shorter wavelengths of light, such as blue and violet, while larger spheres diffract longer wavelengths, such as red and orange.

The intensity and variety of colors seen in an opal depend on the size and arrangement of these spheres, as well as the clarity and transparency of the opal material itself. Precious opals exhibit a strong and varied play of color, while common opals, which lack this ordered structure, do not display opalisointi. This phenomenon is distinct from iridescence, which is caused by thin-film interference, although both can result in shimmering colors. Opalisointi is a unique characteristic of opals and is highly prized in gemstones. It is a result of the internal structure of the mineraloid, not a surface effect.