Boulder Opal (two parts) of 535g on brass base -Australia-
PUMI2513
An Australian curiosity: a precious Opal Vein (Opale AG) in its matrix. From Boulder in Queensland, Australia. What was the bottom of a shallow sea in the Cretaceous, became a layer of amber-coloured sandy clay: the matrix of an Opal. The opal is made up of tiny spheres of silica of different sizes that have agglomerated during wet and dry periods.
