Opal (Neslite variety)
Image: <a href="//commons.wikimedia.org/wiki/User:Archaeodontosaurus" title="User:Archaeodontosaurus">Didier Descouens</a> (CC BY-SA 4.0)
Mineral NameOpal (Neslite variety)
Chemical FormulaSiO2·nH2O
Mohs Hardness5.5
Crystal Systemamorphous
Lusterwaxy
Streak Colorwhite
Cleavagenone
Fractureconchoidal
Specific Gravity2.1
Colorswhite, pale beige
Transparencyopaque
Type LocalitySt Ouens, Paris, France
Mineral GroupSilicates
Usescollector's item
Associated Mineralschalcedony, limonite, goethite
Raritycommon
Description
A rounded, massive specimen of white to pale beige opal, exhibiting a dull to waxy luster and a somewhat uneven surface texture.
Geological Context
Opal forms from the precipitation of silica-rich solutions at low temperatures, often found in sedimentary rocks, volcanic ash beds, or as a replacement mineral in fossils.
