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Until the 19th century its mines were the only source of precious opal available to Europeans.
It is not a play of color as seen in precious opal but rather an effect from microscopic inclusions.
Most of the precious opal is partial wood replacement.
Triplet opals therefore have a more artificial appearance, and are not classed as precious opal.
A guide to Australian precious opal.
Common opal, called "potch" by miners, does not show the display of color exhibited in precious opal.
A gold ring featuring a large girasol, an orange-yellow variety of precious opal, gleamed faintly in the light.
This is most apparent in the precious opal which is capable of displaying a veritable kaleidoscope of colours.
It is the regularity of the sizes and the packing of these spheres that determines the quality of precious opal.
The micrometre-scale spheres that make up precious opal are made of cristobalite, crystallized metastably at low temperature.
The town is sometimes referred to as the "opal capital of the world" because of the quantity of precious opals that are mined there.
Precious opal shows a variable interplay of internal colors and even though it is a mineraloid, it has an internal structure.
The discovery of the ordered sphere structure of precious opal led to its synthesis by Pierre Gilson in 1974.
The internal structure of precious opal makes it diffract light; depending on the conditions in which it formed it can take on many colors.
Deep Blue Sea is made of Australian wool felt on a wire armature and features 26 carved natural precious opals set amidst swaying feathers.
The precious opal is hosted and found within a subsurface horizon or zone of bentonite in-place which is considered a "lode" deposit.
"Noodling: The practice of sifting through rejected mullock heaps for small pieces of precious opal inadvertently discarded by the miners.
Deep Blue Sea drew media attention for its extravagance and for its high value both as a hat, and as wearable precious opal.
At micro scales precious opal is composed of silica spheres some 150 to 300 nm in diameter in a hexagonal or cubic close-packed lattice.
Precious opal and potch opal are generally varieties of this, the difference being in the regularity of the sizes of the spheres and their packing.
Stabilized suspensions of such sub-micrometre spherical particles may eventually result in their self-assembly-yielding highly ordered microstructures reminiscent of the prototype colloidal crystal: precious opal.
"So then the prince and Marrow Bones went to beard Draco Dragon in his den, where he hoarded my precious opal together with another he had.
Other significant deposits of precious opal around the world can be found in the Czech Republic, Slovakia, Hungary, Turkey, Indonesia, Brazil, Honduras, Guatemala, Nicaragua and Ethiopia.
There were colours and patterns within its depths, too, and they resembled the shifting lines of sand on a wave-swept beach, or the flickering flames of a camp fire, or the play of colours in precious opal.
Deep Blue Sea is a hat designed by Australian milliner Ann-Maree Willett, made from Australian wool felt and set with 26 precious opals from Lightning Ridge, weighing a total of 1447.5 carats.
