| ‘THE HAWKESBURY SANDSTONE. 
rounded and abraded. By abrasion I mean that sort of opaque — 
q 
4 
: 
. . : 
which is seen in ground glass. Even grains of tra ‘ 
were angular and not abraded. : 
The reason why the sands derived from the Hawkesbury rocks 
are occasionally so little like the original constituents, is becausé 
they are the result of decomposition from a roc composed 
of fine dust, which has now become compact.* When granite 
decomposes, the sand resulting does not consist of separate , 
of quartz, felspar, and mica, but rather the angular grains conta 
portions of each of these minerals. This I have seen from 
intermediate range called the Little Liverpool Range, an pov 
sandstone formation many hundred feet thick. I can oT 
coarse in places, and consists of light brown opaque 
loosely cemented together with opaque siliceous cement. 
particles are nearly all abraded, and some quite rou! 
Main ge is composed of a similar rock, five oF six 
Livet 
much more so by the outpouring of lava which has 0¥ 
tertiary times 
: Philips 16S 
_ Recent contemporary observations—Mr. J. A. how 
shown in his paper on the History of Grits and Sandstones sok 
| * large number of the carboniferous Permian and Trias pave 
stones are composed almost entirely of quartz crystals aspen 
* Tn 
: . the examination of sands from the Blue Mountains Ct gal 
taken to scrape the material from the rock itself. Sands found 9" 
and water tables by the railway are derived for the. most ere 
s ‘surface and broken up by the transit into 
- $ Quart. Journ, Geol, ‘Soc., vol. 37, p. 6 et seq» 
