Dendritic opal (merlinite) cabochon 13.9g, Madagascar

Opal - dendritic (merlinite)

Dendritic opal (moss opal, shrub opal) - white, opaque and is permeated with a network of fine black dendrites (oxides or hydroxides of iron or manganese). Opal is a mineral, a hydrogel with a fluctuating water content, whose chemical formula is SiO2. n H2O. Water here is most often represented between one and three percent by weight, but in some cases it can reach up to 20 percent.