54 



TORBANITE (KEROSENE SHALE). 



A fragment of this mineral (sawn by Mr. Payne from a 

 larger portion) also formed a part of the collection from 

 Cape Banks. It is brownish-black in colour, has a dull lustre, 

 and burns freely when a lighted match is applied to it. It is 

 identical with the mineral torbanite which is mined at Hartley 

 and other, places in New South Wales, where it is used for 

 the production of mineral oil, and is also sometimes exported. 

 There can be no doubt that the piece in question has come 

 from some vessel trading along the coast, and which by some 

 means had fallen overboard. The Government Geologist, Mr. 

 L. Keith Ward, mentions two other instances in which the 

 same mineral substance has been found on the South Aus- 

 tralian coast; one of these was on the beach at The French- 

 man, Eyre Peninsula, and the other at the head of the Great 

 Bight.*".) 



III. Salt a Cause of Mechanical Disintegration or 

 Rocks in Arid Regions. 



When visiting Stuart Creek pastoral station in 1904, by 

 the kindness of Mr. W. Oliffe, the manager of the station, 

 I was taken over some extensive opal deposits on the run. 

 These were situated to the northward of Pidleeomina Water- 

 hole, in the neighbourhood of Charlie's Swamp, about 30 miles 

 to tne south-eastward of the head station. The opal deposits 

 occur in the upper portions of the cretaceous clays, and are 

 distributed over a strip of country several square miles in 

 extent. They occur usually as thin reticulating veins, or as 

 cylindrical bodies, which in some examples reach a diameter 

 of 12 in. The opal lacks "fire," and is therefore of the common 

 variety, but some of the specimens are beautifully tinted, of 

 various colours, and translucent, resembling the fancy jellies 

 produced by culinary art. 



A very fine example that was exhumed in my presence 

 was in the form of a tree trunk, 2 feet in circumference, 

 possessing some indication of woody structure. The outer 

 portions are milk white, shading off to a delicate pink, and 

 the centre consists of transparent opal of a saffron colour. A 

 fair-sized segment of this opalized tree was secured and 

 brought to Adelaide, but in a short time the greater portion 

 of the specimen cracked and fell to pieces. A few of these 

 spHntered fragments were about an inch in diameter, but 

 the greater part of the disintegrated opal consisted of an 

 innumerable assemblage of small splinters. This intimate 



(ii) Loc. cit., p. 21. 



