Sunday, 27 August 2017

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 colour play 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, the 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.

As the sea regressed, a rare episode of acidic weather was taking place, exposing pyrite minerals and releasing sulphuric acid.
Black opal is the rarest and most valuable. It is generally found as a bar 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.

95% of the world's supply of this radiant, dark lustrous gem is mined at only two pinpoints on the globe - Lightning Ridge and Mintabie, Australia. Between 100 million and 97 million years ago, Australia’s vast inland sea began retreating.

The world famous black opal field of Lightning Ridge was discovered in 1903 and is still producing gems.


As the surface of the basin dried further and cracked, silica-rich gel became trapped in the veins of the rock. Over eons, the silica solidified to form opals. Coober Pedy is often called “The Opal Capital of the World.” The discovery of gem opals sparked a rush of mining activity that has generated top-quality gems for the past 100 years.
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.
Billed as the “finest opal ever,” the Virgin Rainbow made its world debut at the South Australian Museum in Adelaide as the centerpiece of a larger exhibition to commemorate the centenary of opal mining in Australia.
Veteran miner John Dunstan is credited with discovering the Virgin Rainbow in the desert soil of Coober Pedy in South Australia in 2003.

Dustan has mined opals for 50 years, but the internal fire of the Virgin Rainbow is unlike anything he’s ever seen.

Gibber plain near Coober Pedy
Dustan explained that the Virgin Rainbow is a Belemnite pipe, which is essentially an opal that formed in the skeleton of an extinct ancestor of the common cuttlefish. As Dustan cleaned it off, he realized he made a once-in-a-lifetime discovery.

“I knew it was one of the best ever,” he said. “You’ll never see another piece like that one, it’s so special.