BY H, 1. JENSEN, D.SC. 185 



The Australian coalfields were probably in most cases 

 formed by the decay of plant life in swampy freshwater 

 areas. 



There is strong evidence that considerable plant life, 

 sufficient to give thick coal deposits, existed in parts of 

 Eastern Australia, as far back as the Silurian period ; but 

 the deposits then formed have been changed to graphite 

 by subsequent regional metamorphism. 



The writer had occasion some time ago to visit a 

 deserted turquoise mine, near Bodalla, on the South Coast 

 of N.S.W. He observed that the turquoise (AlPO^-Al 

 (HOji + HgO), existed in the form of small segregations, 

 together with pyrites in a graphite bed, associated with 

 quartzites above, and black slate below, of Silurian age. 

 The copper and iron (in part) had evidently' been introduced 

 during the metamorphic processes, and the former had 

 chemically combined with the phosphoric acid present 

 in the organic matter, which probably was a coal bed at 

 the time. The same metamorphic processes that produced 

 the mineralisation changed the coal to graphite. 



The association of the graphite with quartzite, like 

 coal with sandstone, renders it more probable that the 

 oarboniferous matter was of plant, than of graptolitic 

 origin. 



(6.) Oil Shale. In N.S.W. , the chief oil shale deposits 

 oonsist of algal remains [32] (Reinschia Australis), and 

 were probably a freshwater deposit. 



The Tasmanian '* tasmanite " deposits are supposed 

 to have formed in salt or brackish water. 



The conditions for the preservation of oil shales are 

 the same as for coal. 



Petroleum oils have not yet been tapped in Australia, 

 but there are strong possibilities that such will yet be 

 found. 



The conditions for the formation of petroleum oils 

 are {a) the existence of beds of coal, oil shale or other organic 

 remains ; (6) regional metamorphism of just sufficient 

 intensity to give rise to folds and sufficient heat to sublime 

 the oils into the anticlinal maculae, or (c) volcanic intrusions 

 oausing the distillation of organic rocks. 



In south-eastern Queensland oil may yet be found 

 in the Triassic Walloon coal measures under the Birnam 



