Opal

Opal is a solidified silicic acid gel, chemically a water-containing, weakly crystalline version of the mineral cristobalite belonging to the class of oxides-hydroxides. We distinguish different versions, some of them: milk opal-white, mesopal-honey yellow, fire opal-orange, red, red, liver opal-brown, noble opal - the "flash" of different colors in the stone, black opal, like noble opal, only "flashes" from a dark base ” who are the colors, wood opal-opalized wood, you can usually see the structure of the wood, its fibers, and also the annual rings. It occurs in volcanic and sedimentary rocks, it is a spherical, pitted, clustered crack filler, but sometimes it can also form mask shapes on other minerals and fossils.

Places of occurrence: Australia, Mexico, United States, Peru.