BOULDER OPAL ROUGH
Boulder Opal Rough rock. A large sized Opal specimen in Purple, Blue and a splash of Green colour. A really lovely piece of Aussie stone. This specimen is from quality Boulder Opal gemstone. You can see two good seams on opposite ends and who knows what’s on the inside.
10.2cm x 7.2cm x 7.8cm, 710g.
Hydrated Silicon Dioxide.
Opal has been a popular gem for many centuries and has a very interesting structure. The name opal comes from the Sanskrit name for precious stone upala. Opal structure is not crystalline and considered a mineraloid. 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.