Blue Opal

Opal

Opal is a hydrated amorphous form of silica (SiO2·nH2O); its water content may range from 3% to 21% by weight, but is usually between 6% and 10%. Due to the amorphous (chemical) physical structure, it is classified as a mineraloid, unlike crystalline forms of silica, which are considered minerals. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl, and basalt.

Blue

Blue is one of the three primary colours in the RGB (additive) colour model, as well as in the RYB colour model. It lies between violet and cyan on the spectrum of visible light. The term blue generally describes colours perceived by humans observing light with a dominant wavelength between approximately 450 and 495 nanometres. The clear daytime sky and the deep sea appear blue because of an optical effect known as Rayleigh scattering. An optical effect called the Tyndall effect explains blue eyes. Distant objects appear more blue because of another optical effect called aerial perspective.

blue

Adjective

1. Of a blue hue.
2. Depressed, melancholic, sad.

Noun

1. The colour of the clear sky or the deep sea; the colour midway between green and violet in the visible spectrum and one of the primary additive colours.
2. Anything coloured blue, especially to distinguish it from similar objects differing only in colour.

opal

Noun

1. A mineral consisting, like quartz, of silica, but inferior to quartz in hardness and specific gravity, of the chemical formula SiO2·nH2O.