BOULDER OPAL SPHERE
An amazing Boulder Opal Sphere! Featuring beautiful seams of swirling colours of opal amid the host rock. Showing thick seams of great coloured Opal, this specimen is outstanding and very collectable.
Boulder Opal is a variety of Precious Opal found in Queensland, Australia, as cracks or coatings in and around ironstone/sandstone boulders. Opal has been a popular gem for many centuries and has a very interesting structure. The name opal probably is derived from the Sanskrit name for precious stone- upala.
Opal is considered a mineraloid because this structure is not truly crystalline. The chemistry of Opal is primarily SiO2 and varying amounts of water. The amount of water varies from 5 -10% and greater. This water can help geologists determine the temperature of the host rock at the time the opal formed.
Sphere 8.4cm diameter, 862g.
Opal: SiO2 · nH2O Hydrated Silicon Dioxide.