192 Henry C. Richards: 



Coarse-grained.— T\i\^ stone is of the same nature as the 

 iine-grained one, but has a much coarser grain, and a good deal 

 more argillaceous material all through it. The grains are 

 angular, very uneven in size, .7 mm. to .07 mm. in diameter, 

 und large isolated patches of the fine-grained matrix occur. 

 This matrix is present to the extent of about 25 per cent., and 

 patches 1 mm. in diameter occur. The microscopic characters 

 indicate only fair weathering properties, and a low crushing 

 strength. 



Qreendale Stone. 



This has much tlie same microscopic character as the coarse- 

 grained Egerton stone, but in addition has scattered through it 

 specks of ferric oxide, which give the stone a light biown 

 ■colour. (See Plate IV., Fig. 2.) 



CHEMICAL ANALYSIS. 



Chemical analyses w-ere carried out by the author on all the 

 sandstones, with the exception of the Stawell stone. The 

 analysis of that stone in the following list was made by the Vic- 

 torian Mines Department. ^ 



In all cases samples for analysis were taken from material 

 uniform with that used for the other tests. For stones of 

 -aqueous origin like these sandstones a chemical analysis does 

 not carry so much weight as for igneous rocks, because in the 

 former uniformity in either chemical or physical characters of 

 even closely adjacent beds is not to be relied upon, whereas in 

 igneous rocks which have cooled from a molten magma, uni- 

 formity of composition is much move likely. However, chemi- 

 cal analyses of these stones, while only holding for the particu- 

 lar beds of which they are samples, serve to indicate in general 

 the composition of the stones, and what constituents are liable 

 to alteration during weathering; this information used in con- 

 junction with the other tests is often of great value. 



2^he Staivell Stone is seen to be a very highly siliceous one, 

 and to be made up almost entirely of silica in the form of sand 

 grains. The combined water, alumina, and a certain amount of 



Ann. Report Sec. for Mines, Victcjiia, 1907, }>. (3;J. 



