34 Reviews — North Queensland Tin-fields. 



Leases, unfortunately without good results, though they were 

 continued through the old crystalline rock to a depth of over 

 1,000 feet in two cases. Among the special reports, accounts are given 

 of the working of precious opal in Stuart's Eange in the centre of 

 South Australia, manganese ores at Pernatty Lagoon, boring for oil 

 near E.ohe, and details of various copper-mines, most of which are 

 not now working. 



The precious opal occurs in the Desert Sandstone of Upper 

 Cretaceous age, as it does in all the other opal-fields of Australia, 

 which, like the Stuart's Range field, are all situated just inside the 

 region, which has a rainfall of 15 inches per annum. It occurs in veins 

 and patches associated with large amounts of common opal, and 

 seems to have been formed in a similar manner to that in which 

 surface quartzites and limestones are formed in similar dry regions. 

 The amount of the precious variety is not large, but good finds are 

 made. The Pernatty Lagoon manganese deposits seem to be a 

 valuable field of this metal. The ore, which contains from 64 to 81 

 percent of Mn Oo, with a certain amount of ferruginous material, 

 is associated with a dolomite of uncertain age, and is found generally 

 along the master joints. A considerable quantity of ore has been 

 raised, and more would be sent away but for difficulties of transport 

 in a rainless country. 



!N^ear E,obe a bore has been sunk to a depth of 3,950 feet in search 

 of oil. The district was the subject of a report in the last review of 

 raining operations (No. 24). In this report the Government Geologist 

 reported very unfavourably on the oil prospects, and his conclusions 

 seem to have been substantiated, since after passing through Tertiary 

 limestone, with gravels and lignite, and Jurassic carbonaceous shales 

 to the depth above-named no signs of oil have been seen, except 

 a little natural gas. Of the copper-mines reviewed, some seem still 

 to have good reserves of ore ; many were abandoned owing to 

 shortage of labour in the days of the gold rush in 1851, and not owing 

 to failure of ore supplies. The present time, when the price of 

 copper is so high, seems to be a favourable opportunity for restarting 

 some of these concerns. 



W. H. W. 



IX. — North Queensland Tin-fields. 



Geology and Minehal Resources of the Cooktown District Tin- 

 fields (North Queensland, 1914). By E. Cecil Saint-Smith, 

 A.S.T.C., Assistant Government Geologist, Queensland Geological 

 Survey, pp. 211, with 3 maps, 4 figures, 59 plates, and 3 plans. 

 Brisbane, 1916. 



THE Cooktown district tin-fields are situated in a hilly region, 

 about 36 miles long, along the east coast of Queensland, running 

 south from Cooktown at the mouth of the Annan River. The country 

 is composed of slates probably of Gympie (Permo-Carboniferous) age, 

 invaded by large masses of granite, with a few flows of post-Tertiary 

 basalt and alluvium of two different ages. The tin-ore is found 

 in the alluvium, both old and new, and is disseminated through 



