152 A Physical Description 



are the most abundant in which the quartz preponderates 

 over the mica, frequently passing into a homogeneous 

 quartz rock. The greater part of these beds possess a very 

 foliated structure, with a lamination in general definite 

 directions. There are no quartz reefs in connection with 

 these deposits. Whatever quartz there is exists in the form 

 of bed rock, and is part of the whole altered strata. 



There can be no doubt that these belong to some formerly 

 stratified rocks lying below the Silurian, or even the 

 Cambrian. They are too much altered to contain fossils, 

 if, indeed, they ever did possess them. It is very singular 

 that there are no quartz reefs in connection with them. The 

 beds contain gold in small quantities. Possibly the meta- 

 morphic action which changed them from the stratified 

 state has been too partial or limited to segregate thoroughly 

 the gold and quartz into reef deposits. The metamorphism 

 to which they have been subjected is due to — 1. The 

 pressure to which they have been subjected when covered 

 by great masses of formations, which have subsequently been 

 nearly all denuded away ; 2. Heat accompanying that 

 pressure ; 3. Water also much compressed and heated. 



Silurian. — At the base of the western half of the Eldon 

 Range, and extending southwards to the Collingwood 

 Valley, certain strata are found a considerable thickness of 

 dark grey mudstones and clay slates with slight admixture 

 of arenaceous rocks, and towards the base calcareous bands 

 and limestones. The dip is not easily ascertained, from the 

 cleavage which affects the upper beds and the contortion of 

 the lower ones. Succeeding these are highly micaceous beds, 

 siliceous grits and clay slates, the latter resting uncom- 

 formably upon the metamorphic rocks. On the north shore 

 of the Macquarie Harbour, and the course of the Gordon 

 River for thirty miles from its mouth, and for a short distance 

 of the courses of the King's and Franklin Rivers, and on 

 the line of country between the Eldon Ranges and the West 

 Coast, the usual upper paleozoic and greenstone formations, 

 so common on the east side of the colony, are absent. 

 Their places are taken by several marked divisions of the 

 Silurian rocks, but their exact sequence has not yet 

 been determined. According to Mr. Charles Gould they 

 are chiefly of Silurian, and some of them of Cambrian 

 formation. The most prominent formation consists of 

 fossiliferous limest^pes, the entire thickness of which is not 

 less than 1000 feet, called by Mr. Gould the Gordon 



