Fire opal 11mm round 4.42ct

Fire opal is a gem-quality form of amorphous hydrated silicon dioxide with no crystalline structure. Like other opal gemstones, between three and ten percent (and in some cases as much as 21 percent) of the weight of fire opal is water. Owing to its high water content, fire opal is rather delicate and should be protected from heat and prolonged exposure to strong light, to avoid drying and cracking. Fire opal is not known for its play of colour, but rather for its vivid body colour. In fact, most fire opal does not exhibit any play of colour, although it may occasionally exhibit flashes of bright green.

The name 'fire opal' is derived from its 'fiery' orange colour, though it can also be white or brown. Darker brownish fire opal will typically exhibit more play of colour than fiery golden coloured varieties. Fire opal that exhibits no play of colour is sometimes referred to as jelly opal. Unlike most opal, fire opal occurs with good transparency and because of this, it is usually faceted rather than cut en cabochon. On the other hand, brownish fire opal is usually cut en cabochon to enhance and maximize its desirable play of colour effect.

Fire Opal Gemological Properties: Back to Top

Chemical Formula: SiO2_nH2O Hydrous silicon dioxide Crystal Structure: Amorphous; kidney or grape-shaped aggregates Colour: Yellow to orange, orange-red Hardness: 5.5 to 6.5 on the Mohs scale Refractive Index: 1.37 to 1.52 Density: 1.98 to 2.50 Cleavage: Indistinct
Transparency: Transparent to opaque Double Refraction or Birefringence: None Luster: Subvitreous to waxy, resinous Fluorescence: Usually none