BOULDER OPAL GEM SPECIMEN
A stunning Boulder Opal Gem Specimen for the collector. This gem shows great green, orange, pink, blue and purple hues in normal light. It is quite rare that it has been kept as a specimen and not made into jewellery as most colourful Opals are. Valued at $880, this is a bargain price for a beaut Aussie gemstone.
3.3cm x 2.5cm x 1cm, 54.46ct.
Opal: SiO2 · nH2O Hydrated Silicon Dioxide.
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 (quartz) and varying amounts of water. The amount of water varies from 5 to 10% and greater. This water can help geologists determine the temperature of the host rock at the time the opal formed.