100 



are often found in sandstone country, and therefore, of course, of 

 no value. Fossils were not found in this formation, but it is 

 probably identical witli the " desert sandstone " of the JSTorthern 

 Territory of Australia. 



Paleozoic or Akcii^:an Hocks. — The main components of the 

 crystalline rf)cks are the liornblendic schists and slates in difierent 

 varieties. They immediately overlie the granites, and are over- 

 lain by the feldspathic schists and (juartzites of the same forma- 

 tion. In this order of superposition they were found outcropping 

 by travelling in a north-easterly direction from Fraser Range, 

 where they are well developed, and also eastwards of the Annean. 

 As components of less importance of the same formation must be 

 mentioned here talcose and micaceous schists, whilst on the 

 other hand a siliceous ironstone, locally called "jasperoid," is 

 constantly and largely developed in this series. The latter is a 

 frequent occurrence in aurifei'ous country. The quartzites 

 occupy also a prominent position amongst the Paheozoic forma- 

 tion. They are mostly of a hard glassy character, with a bluish 

 tint; the gritty variety though is also found, especially eastwards 

 of Yilgarn. The quartzites and the underlying feldspathic and 

 hornblendic schists seem to be comformably stratified, and are 

 only in a small degree disturbed from their horizontal stratifica- 

 tion. 



Plutonic. — The immense area occupied by granites represents 

 this formation. Wherever outcropping they bear a most distinct 

 eruptive character. Of a dome-like form and of moderate height, 

 say, on an average, about 200 feet, they often show signs of a 

 macro-fluxional structure, the big curves formed by the white 

 feldspar crystals being strikingly discernible. They are frequently 

 traversed by quarts veins or dykes of a magma differently grained 

 to the main mass, but these veins, of course, are of no importance 

 from a prospecting point of view. A puffing up of big pieces, or 

 a peeling off of scales of these granites, which is of common 

 occurrence, may be due to the action of a sudden change of heat 

 and frost, a dynamical factor of great importance in this country. 

 Generally these granites are poor in plutonio intrusions, and if 

 they occur, they are of a dioritic nature. 



Plutonic and trappean rocks other than, diorite are found in 

 the country round Lake Lefroy. There diabase and diabase- 

 porphyry occur. The Parker Hills, on the south shore of Lake 

 Lefroy, are at their eastern end composed of the latter material, 

 and the former form huge dykes in the above-mentioned country, 

 also occasionally they appear rising in bizarre mases, through the 

 basins of the salt lakes of this country. 



The Canning Hills (Mr. Broad's Station) show signs oi fre- 

 quent plutonic intrusions, and deposits of detrital eruptive 



