Friday, 1 November 2013

Black Opal

In the first century A.D. Pliny wrote of the opal, "... For in them you shall see the living fire of the ruby, the glorious purple of the amethyst, the sea green of the emerald, all glittering together in an incredible mixture of light", and later Shakespeare was to describe it as the "Queen of Gems".

Due to its unique colour play and its "life", the opal has been subjected to many superstitions and myth . Opal was said to ward off diseases and for this reason was worn in amulets. In Roman times it was included in the crown of the Holy Roman Emperor.
Opal, from the Greek, "Opallos", meaning 'to see a change (of colour)', is a formation of non-crystalline silica gel.

Millions of years ago, this gel seeped into crevices and cracks in the sedimentary strata. Through eons of time and through nature's heating and moulding processes, the gel hardened and can today be found in the form of opals.

Black opal is the rarest and most valuable type. It is generally found as a bar (or bars) of various colours forming natural water horizontals in dark grey to black "potch nobbies" or "nodules". The unique patterns are as complex as an artist's imagination.
99.9% of the world's supply of this radiant, dark lustrous gem is mined at only two tiny pinpoints on the globe - Lightning Ridge and Mintabie, Australia.
The world famous black opal field of Lightning Ridge, N.SW. was discovered in 1903 and is still producing many beautiful gems. The discovery of light opal in 1915 made famous the name of one of the most hostile and remote places on the Australian continent - Coober Pedy, S.A., the largest opal producing centre on earth.
Coober Pedy, an Aboriginal name meaning "White man in a hole", adequately describes the mines and miners' dwellings - burrows dug into the scarp, in order to escape the soaring temperatures of the day and the freezing winds at night.

Australia's Oldest Mammal. - STEROPODON GALMANI new genus and species.
Age and Formation: Early Cretaceous Griman Formation. 100 - 146 million years ago.
Locality: Lightning Ridge, northern New South Wales.
Derivation of name: Steropodon comes from the Greek words meaning 'Flash of lightning' and 'Tooth"; the other name, galmani, acknowledges the contribution made by Dave and Alan Galman in saving this unique Australian fossil for science.

Description: Part of right lower jaw with three molar teeth in place. The original bone and tooth material has disappeared and been completely replaced by silica (opal), preserving every detail.

Interpretation: The presence of several cusps on the teeth show that they belong to a mammal. The cusp pattern indicates that Steropodon is related to Australia's living Monotremes, the egg laying Platypus and the Echidnas. Australia's opal fields have produced many interesting examples of opalised fossils and remains of long extinct animals and plants. Opalised fossils are often, unfortunately, cut up for their opal content, jewelry or sold as curio's to tourists and any scientific information they contain is irretrievably lost.