BY A. MONTGOMERY, M.A. 



191 



decomposed wherever I have met with them that it is quite 

 impossible to name the rock with any accuracy. As far as 

 can bo judged from the decomposition products, it must have 

 been chiefly composed of felspar and hornblende without free 

 quartz, and is likely therefore to be a diorite or hornblende 

 andesite. Till further research reveals its true nature we 

 may without much inaccuracy speak of it as a dioritic rock. 



I noticed it more especially at the Mount Zeehan and Whyte 

 River Silver-fields, but at Mount Dundas there are also rocks 

 of this series. At Mount Zeehan it is found plentifully on 

 the main road between the Comstock and Silver Queen 

 holdings, some of the belts being close on a quarter of a 

 mile in width. It is notable that the slates in this vicinity 

 are much contorted and broken by small faults, as may be 

 seen in the roadside cuttings. The dioritic rock is most 

 easily distinguished by its coarse granular appearance on the 

 fresh fracture, and by its clayey nature, being almost free 

 from grit. On the surface it forms a stiff yellowish brown 

 clay, quite unlike the dark red-brown clay resulting from the 

 weathering of the serpentines. In the Argent, Balstrup's, 

 Silver Spray, and Western mines it is cut through by tunnels, 

 also in Evans's section Hr fl > and a dyke of it was noticed in 

 section if-p of the Tasmanian Silver Mining Company. In 

 Balstrup's and the Western mines it clearly occurs as dykes 

 Penetrating the Silurian country slates and sandstones. In 

 the Argent tunnel no lodes were met with in it, but some 

 veins of pyrites and loosely coherent quartz crystals were 

 Passed through. The inner end of the adit is in clay slate, 

 tfl e outer half being in the volcanic rock. This has here 

 much the appearance of a tufa, and may prove not to be a 

 Weathered dyko penetrating the slates, but a tufaceous bed 

 resting upon them. In the lower tunnel of the Silver Spray 

 company the igneous rock is clearly of a fragmentary 

 character, containing numerous angular fragments of clay 

 slate imbedded in the clayey matrix of weathered volcanic 



°ck. Here we probably have a remnant of a tufa bed, 

 most likely one of many that were formerly widely spread 

 over the district. Some quartz veins were found in this 



taoeous rock, and on the surface there is a large mass of 

 gossan, supposed to have been the cap of a lode, until the 



n «f Was driven underneath it and far past the line of it 



II e surface without success. Quartz veins and a lode of 

 i arte of considerable size are also found traversing the 



itie dyke in Balstrup's section, and in the similar dyke 



and" I Wll y te Eiver ou wnich bodkin's, Smith and Bell's, 



the Whyte River company's claims are situated, quartz 



ems have again been found". The outcrops of both these 



ykes, too, are marked by large masses of gossan. It appears 



me that the weathering of the dioritic rock is of itself 



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