190 



NOTES ON SOME GEOLOGICAL OBSERVATIONS, WEST COAST. 



2 IF and 1 §fS apparently forming the back of the hill into 

 the face of which the Mount Dundas Company's tunnel is 

 being driven. Though the serpentine rocks at the Heazle- 

 wood are considerably distant from the above, their similarity 

 in lithological character would lead one to suppose that they 

 also are related to the same series. They first appear on the 

 road from Corinna to Waratak, at about thirty chains past 

 the 21 mile post, at what are called the Eighteen-mile Huts. 

 Prom there they extend on to past the Heazlewood and 

 Heazlewood Extended mines. On the track from the Heazle- 

 wood to the Specimen Eeef mine the serpentine extends to 

 about half-a-mile from the crossing of the Savage Eiver. 

 The stone varies very much in appearance, from a greenstone 

 to almost pure serpentine. Parts of it contain much schiller- 

 spar, and closely resemble gabbro. The appearance of all 

 these serpentinous greenstones is consistent with the theory 

 that the rock is a dolerite or gabbro, with its constituents 

 metamorphosed by schillerisation, or internal chemical change, 

 and by weathering, or external atmospheric influences. The 

 more or less complete alteration into serpentine is probably 

 due to the unequal distribution of olivine in the "original 

 rock. The change of olivine into serpentine would also 

 account for the formation of the magnetic and titanic iron ore 

 so common in portions of the rock. An interesting deduction 

 from the appearance of these greenstones is that they were 

 once very deeply buried, schillerisation being believed to take 

 place only at great depths. It is possible, then, that these are 

 the roots of one time mighty volcanic masses, possibly covering 

 the western side of the island with their lavas. The microscopic 

 study of these rocks promises a most fascinating field for the 

 petrologist. Should there prove to be grounds for the idee. 

 I have advanced, that the volcanic rocks were once much more 

 widely spread than now, the mineral nature of the country 

 would be to some extent explained, the conditions being then 

 such as may be presumed on many grounds to have been 

 favourable for the formation and filling of mineral veins. 

 Every fact that can be adduced to illustrate the history and 

 relations of these intrusive masses will be of service to the 

 cause of geological science in many ways. It has occurred to 

 me that these old matamorphosed igneous masses may 

 possibly represent the lower members of the great greenstone 

 flows that have covered so much of the colony. 



Throughout the mineral fields of Mount Zeehan, Mount 

 Dundas, and the Heazlewood, there is another set of igneous 

 rocks that appear to be of quite different character from the 

 greenstones. They seem to be closely connected with the 

 mineral veins, and when more is known about them, I am 

 inclined to believe that the connection will be found to be 

 even closer than it at present appears. They are so much 



