262 E. 0. Thlde: 



The common opal is present only in small quantity, and of no 

 particular interest. It is clearly secondary. The age of the 

 serpentine will be referred to later. 



(2) Sediments Composed Largely of Serpentine Detritus. 



These deposits vary from coarse or waterworn conglomerates 

 to fine-grained, hard banded rocks. 



The conglomerate has been referred to in a previous paper. 

 It can be examined at two outcrops, namely, at the Monument 

 Gap and in the bed of the Dolodrook Eiver, above Thiele's Creek 

 junction. 



In both places it lies along the south-western margin of the 

 serpentine belt. At the Monument Gap, both the boulders and 

 the matrix consist almost entirely of serpentine. Mechanical 

 deformation and differential movement have squeezed and 

 striated the boulders, but the evidence of aqueous origin appears 

 to be still fairly pronounced. 



In the bed of the Dolodrook, however, some finer beds are 

 associated, containing some rounded and sub-angular fragments 

 of a compact black rock suggeisting at first sight black slate, 

 but microscopic evidence shows this rock is a fine-grained, 

 igneous one, and the matrix consists of serpentine and numerous 

 fragments of pjTOxene. 



These beds dip westerly at a high angle, and overlie the 

 coarser conglomerate which flanks the serpentine. A little 

 further west, lower down the Dolodrook, the black graptolite 

 slates form a bluft". The relation to the detrital serpentine 

 rocks is not clear, but they appear to overlie them, which is in 

 conformity with observations in other parts. In Roan-Horse 

 Gully, east of the chromite occurrence, the fragmental beds are 

 again exposed, and here portions show considerable calcification, 

 some portions being of the nature of ophicalcite. An analysis of 

 this material was made by Mr. Ampt. 



Carbonate of Lime - 4-1.09 



Silica - - - - 24.70 

 Alumina - - - 4.22 



Ferric oxide - - - .75 



Ferrous oxide - - 5.36 



Lime - - - - 3.99 



