Home' Stuart Highway Guidebook : Stuart Highway Contents Geology of Opal
All precious opal in South Australia occurs in rocks affected by
weathering during the Tertiary Period (1.8 to 70 million years ago)
and probably deposited 15-20 million years ago. The weathering
process broke down minerals of the country rock to produce
kaolin (clay) and soluble silica and created cavities in the rock by
dissolving out soluble minerals, and fossils. Periodic lowering of
the water table carried the silica-rich solutions downwards leaving
deposits in the cavities and fissures, creating opal.
Colour in precious opal is caused by the regular arrangement of
silica spheres diffracting white light, and breaking it up into
spectral colours. Opal colours depend on the angle of light and
can change or disappear as the gem is rotated.
Historic cottages at Andamooka
The Umoona Museum and film The Story of Opal
Old Timmers Mine
Fay’s Underground Home in Coober Pedy
Photos courtesy Coober Pedy Historical
“No other gem can compare for an instant with the opal in
its depth of colour, in its infinite variety, and in that changing
mystery of loveliness,” wrote Tully Wollaston in 1924.“Those
glorious lights, one must realise, are not the ordinary hues of the
diamond and prism, but far softer and deeper tones which
burn and glow with a steady flame.”
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Opal has a long history. It was mined in Hungary and
Mexico and the Spaniards returned with opal from the
Aztecs in South America. Opal artifacts, were discovered in
Africa. The Romans prized opal above all gems. Mark
Antony coveted Nonius’s opal ring for Cleopatra. Nonius,
however preferred exile rather than part with his treasure.
Australian opal with its vibrant colours is the best in the
world. Opal was first discovered in Australia by geologist
Johannes Menge near Angaston in the Barossa Valley in
1849, followed by Opalton (Q) 1896, White Cliffs (NSW)
1899, Lightening Ridge (NSW) 1905, Coober Pedy 1915,
Mintabie in the 1920s and Andamooka in the 1930s.
Life was tough for the early miners. Opal diggings were
isolated and lack of water was a huge problem. Miners, dug
shafts about three metres down to find opal. A hand
windlass and bucket were used to bring ore to the surface.
Tully Wollaston, from Adelaide, was the world authority
on opal. He was instrumental in pioneering the Australian
opalfields and made over 25 trips to Britain, Europe and
America promoting opals. Tully studied precious gems and
was captivated by opals. He considered opal combined the
best qualities of all jewells and was the gem of the future.
After hearing of an exciting opal find in November 1888,
Tully travelled by camel through the interior to Queensland.
It was the height of summer in a drought year and there were
dead and dying stock near all the waterholes.
Day after day he travelled relentlessly, enduring a rayless
sun; every diary entry the same -“Heat awful” . One day,
crouching over the saddle, he came to the end of his tether.
Then the sight of that patient old head held wearily aloft as
the camel plodded painfully along set his blood humming
again. He promised him a week’s rest when they arrived.
Finally, after six weeks crossing half a continent, Tully
reached the diggings and was thrilled with the parcel of opal.
On Tully’s first trip to London there was no opal on the
market and most jewellers were reluctant to stock it. Tully
went from shop to shop exhibiting the beautiful stones and
extolling their virtues. Eventually he found a firm eager to
give this new sandstone a chance. As time went by, overseas
markets expanded and opals became in high demand.
In 1915 opal “floaters” were found in Coober Pedy by
14 year old Willy Hutchison, accompanying his father with
a gold prospecting party. Because of lack of water, the party
left before locating any opal seams. Tully equipped another
expedition and they searched for months The weather was
scorching hot so they dug a shelter into the side of a hill.
After their camels wandered off, they started walking back to
civilisation, carrying their remaining water on their backs.
Luckily they met brothers Jim and Dick O’Neil who had
heard of the opal find and had come from Tarcoola in a dray
with 100 gallons of water to try their luck. The disenchanted
“would be miners” bartered their camp and the lost camels.
The O’Neil brothers took them to safety, then went back to
the opal fields, releasing their horses to return home. They
had exciting opal discoveries. After water ran low, they
trudged 90 miles to Anna Creek Station.
During the First World War, Aboriginals sold black opal
at Coober Pedy, thought to come from Mintabie. In 1976
heavy earth-moving equipment moved in resulting in many
large finds. As Mintabie is on Aboriginal land, a permit to
visit is required and can be obtained at Marla Police Station.
There are different types of opal - Black Opal, ablaze with
colour with a dark background, Boulder Opal from Western
Queensland, White or Light Opal - bright colour with light
background, Matrix opal is treated to enhance the colours.
Opal can be presented as solid opal, doublets with dark
backing added, or triplets where opal is sandwiched between
clear crystal quartz and dark backing.
In 1968 Mr Addyman, an Andamooka opal miner,
unearthed a pile of opalised bones in the ancient sea bed. Mr
Addyman carefully recovered more bones forming a partial
skeleton. It was a plesiosaur – a creature resembling the Loch
Ness monster. The giant marine reptile, over 6 metres long
lived in Australia’s inland sea 120 million years ago when
dinosaurs roamed. The Addyman Plesiosaur is unique and
appears to be a species previously unknown. Such fossils are
no longer recovered as machines have replaced hand tools.
Mr Addyman believed the fossil was a treasure belonging
to the South Australian people and offered it to the South
Australian Museum. The Advertiser bought it and donated it
to the Museum. Origin Energy, the Waterman’s Club and
Coober Pedy Tourism Association sponsored the preparation
process. Ben Kear, paleontologist, spent long hours
researching the plesiosaur and painstakingly removing the
encasing rock. It now has pride of place in the Origin Energy
Fossil Gallery, at the Museum along with other ancient sea
creatures. The display makes fascinating viewing.
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