Opal: the Gem of the Never Never

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T. Murby & Company, 1924 - Frontier and pioneer life - 164 pages
 

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Page 15 - Unequal diastrophic movements then brought about lacustrine conditions on portions of the now uplifted bottom of the old sea and in other portions it permitted the admission of ocean waters resulting in the deposit of the Desert Sandstone formation. Finally a general upheaval...
Page 15 - It rises ten feet above high-water mark, and consists of hard, compact brecciated conglomerate." 2 Geological Observations in British New Guinea in 1891. which it originally extended. . . . After the Rolling Downs formation had been laid down in the comparatively narrow sea which connected the Gulf of Carpentaria with the Great Australian Bight, and converted the Australian area into two islands, a considerable upheaval took place. The denudation of the Rolling Downs formation then followed, and...
Page 15 - ... or 7 miles further away and brought back to water at the camp ; there were besides several deposits more remotely situated which it was quite impossible to approach. The country over which prospecting for opal is carried on extends from the southern boundary of the State to Kynuna beyond Winton, and is practically limited on the east by the termini of the main trunk railways, the mean width being about 250 miles. Within the area above defined I visited about 100 localities where precious opal...
Page 15 - ... traced from Eulo, in the Gunnamulla district, about 150 miles north of Bourke, in New South Wales, for some 500 miles in a north-westerly direction as far as Winton, in the county of Ayrshire. The precious opals met with occur here and there in patches in upper Cretaceous sandstones and clays. In places the mineral is found scattered over the surface, being set free by denudation, but such occurrences furnish little evidence of precious opal below. The average depth of the shafts is 14 feet,...
Page 15 - Grey Ranges rise from beneath it like islands. " Westward and southward it extends across South Australia into Western Australia and New South Wales, but except in Queensland it appears to be covered to a considerable extent by tertiary rocks.
Page 15 - ... further away and brought back to water at the camp ; there were besides several deposits more remotely situated which it was quite impossible to approach. The country over which prospecting for opal is carried on extends from the southern boundary of the State to Kynuna beyond Winton, and is practically limited on the east by the termini of the main trunk railways, the mean width being about 250 miles. Within the area above defined I visited about 100 localities where precious opal occurs, the...
Page 15 - Exploratory drives are sometimes put in, but opal-miners, unless the gem is met with in the shaft itself, as a rule do very little driving, frequently abandoning their shafts without any adequate trial, and often never even piercing the strata above the opalbearing land.
Page 15 - band,' in which the sandstone opal is found, occurs in the falsely bedded series of sandstones and clays at the base of the sandstone, and at its junction with the underlying clay.
Page 15 - The opal which is found may be roughly divided into two classes, known to miners as ' boulder ' opal and ' sandstone
Page 100 - Stuart's Range is the name given to the ridge that constitutes the divide between two systems of surface drainage. The divide extends in a direction having a bearing nearly NW-SE, and separates the basin of Lake Cadibarrawirracanna from that containing Lakes Woorong, Phillipson, and Wirrida. These so-called " lakes " are typical "playas" or "clay-pans

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