Opal (from Latin opalus which probably comes from Sanskrit upalus = "precious stone") is an exceptional mineral that is only amorphous, being a hydrated silicate with the chemical formula SiO2*nH2O.
As the percentage of water can reach 25% as an amorphous solid body, the opal appears like glass without having a crystalline structure.
The mineral frequently appears in nature as the filling of a vein, or as granules. Opals are very rare, so they are not exploited industrially. Opal has been found on all continents but 97% of opals come from Coober Pedy, South Australia.
Not long ago, significant opal deposits were discovered in the Welo region of Ethiopia
The color of the mineral is very variable, from colorless to grey, red, brown, yellow, rarely due to some impurities, orange or reddish copper (called "fire opals").
The variant of "wood opal" is formed by the phenomenon of impregnating wood with silicates
Hydrophane or "water opal" exhibits a play of light colors similar to water.
Opal in Roman culture was considered the "stone of love" or the "stone of hope".
Stone type: Natural Topaz, Shape: Marquise, Color: White, Weight carat: 9.10, Treatment: Untreated, Source: Brazil, Stone Clarity: Eye clean, Stone size mm: 16.00x8.00, Sale information: Lot price, Lot details: Pair for earrings
Product Name: Natural Tourmaline, Shape: Oval, Color: Dark Brown, Stone Dimensions mm: 11.60x9.00x6.20, Stone carat weight Weight: 3.85, Stone Clarity: No Visible Inclusions, Treatment: Untreated, Origin: Sri Lanka
Product name: Natural Tourmaline, Shape: Pear, Color: Dark Brown, Stone dimensions mm: 18.90x10.30x7.00, Weight carat: 9.60, Stone clarity: No visible inclusions, Treatment: Untreated. It is a dichroic stone showing at the same time brown and green colors depending on the angle from which it is viewed.