![]() ![]() ![]() See also Honey Opal.Ī variety of Precious Opal in which the play of color is arranged in a vivid harlequin, diamond-shaped, or rectangular-shaped pattern.Īn unnecessary name for orange-brown opal.Ī colourless variety of Opal. Compare with Girasol Quartz which is named after this material.Ī name for yellow or gold-coloured opal. Originally reported from Holzbrücken mill, Ingering valley, Knittelfeld, Styria, Austria.Ī bluish-white translucent opal with reddish reflections. Transparent mexican Precious Opal with an intense play of colours (red, green, blue and yellow).Ī type of opal that doesn't show any fire.Ī precious opal where the play of colours is only visible when held up to the light.Ī transparent to translucent variety of Precious Opal where the colour play is visible both on the surface and in the interior.Ī red, brown-red to brown-orange, transparent to translucent variety of opal.Ī yellow to orange variety of opal, owing its colour to microscopic inclusions of orpiment and realgar. Green nickeloan variety of Opal transitive to ChrysopraseĪ translucent variety of common opal colored apple green by the presence of nickel. (See also "Andean Opal")Ī variety of Precious Opal found in Queensland, Australia, as cracks or coatings in and around ironstone/sandstone boulders.Ī rare chatoyant form of opal showing a thin line of fire.Ī variety of common or precious opal distinguished by its red-brown color. Cause of colour can be light scattering effects or occasionally microscopic admixture of chrysocolla or other minerals. Translucent blue opal with no play of colours. The most precious kind of opal, this variety of precious opal has a dark background colour. German name for pink opal variety from Peru (Catamarca?).Ī precious opal with bands showing a play of colours. Opal formed of thick mounds deposited from hot silica-rich springs.Ī yellow-brownish variety of Opal, resembling Amber. Visit for gemological information about Opal.Ī variety of Opal with alumina and lime impurities. ![]() The opal-AG studied comprised close-packed silica nanospheres, ~400 nm in diameter. (2022) opal-AN was shown to mainly comprise as aggregates of differently-sized of nanospheres (<5 nm) that form banded features. Studies at low temperature show that water molecules may be organized into an ice-like structure, which includes the cubic ice modification (Eckert et al., 2015). Transitions between opal-AG, opal-CT, and opal-C are common. Opal-AN: amorphous ( Amorphous- Network (found as hyalite). Opal-AG: amorphous ( Amorphous- Gel) (closely packed amorphous silica spheres form a diffraction grating to create precious opal). Opal-CT: contains cristobalite-tridymite Although it is still (2007) regarded as a valid mineral species for historical reasons, opal is not a true mineral in the accepted sense of the word as it is either composed of cristobalite and/or tridymite or composed of amorphous silica. ![]()
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