Total weight of matrix opal approximately 46.96 kilos
Consisting of the following:
Specimen number 1 approximately 25.60 kilos
Specimen numbers 2 to 4, total weight approximately 8.92 kilos
Specimen numbers 5 to 21, total weight approximately 7.91 kilos
Specimen numbers 22 to 25, four bags of slabbed matrix opal, total weight approximately 4.52 kilos.
Koninderie - an Aboriginal name for rainbow.
The Koninderie matrix opal was discovered in Andamooka, South Australia. When discovered the original weight of the matrix opal was 65.7 kilograms, and at the time believed to be the world's largest natural matrix opal. The matrix opal was cut in half in 1975.
A news release in 1975 writes of Mr Bill Moriarty, a Perth gemmologist, being commissioned to cut the specimen with Dr John Daniels as the consulting geologist. According to information available at the time the process took two days to slice through the opal using specially designed equipment. Approximately 10 kilos of opal dust was lost in the cutting process. Of the two pieces, one remained complete, the other half cut into many varying sizes, taking a further six months of cutting.
A significant piece of the opal was exhibited at the Mineral Science Division of the Smithsonian Museum, Washington DC, America in the 1990s.
Matrix opal is a variety of natural opal in which the opal component is intimately diffused throughout the original rock as fillings of pore spaces, or between the grains of the original host rock in which the opal has formed. It is essentially "opal in rock". As such, specimens and stones are cut to include the rock and the opal and presented in one piece. In Andamooka, the matrix can be composed for example, of sandstone and limestone, and other silicified rocks at the location. The precious opal component is amorphous silica that has subsequently in-filled these rocks around micro-crystalline quartz, crystalline quartz grains in the sandstone, and minute cavities within the original limestone rock.
We are most grateful to Anthony Smallwood MSc (UTS), FGAA, GG for his assistance in cataloguing this work.
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