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 a minor seam on one side.
6.6cm x 12.5cm x 10.5cm, 1348g.
nH2O 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.