BY A. MONTGOMERY, M.A. 



18» 



the mass of Mount Heemskirk and the Meredith Eange, and 

 is_ also encountered on the Magnet Range, near Mount 

 Bischoff. As quartz porphyry and eurite it comes in at 

 Mount Bischoff itself. This porphyry is clearly intrusive 

 through the slates there, as fragments of slate and sandstone 

 are frequently seen embedded in it, and the workings of the 

 Mount Bischoff mine also show it ramifying through the slate. 

 One of the problems to be solved is the relation of this 

 porphyry to the main granitic mountain masses ; is it 

 contemporaneous with their upheaval or intruded long 

 subsequent to their formation ? 



The greenstones and serpentinous rocks are of much 

 interest, more particularly as the serpentine at the Heazlewood 

 is itself the matrix in which metallic lodes are found. There 

 is probably more than a mere coincidence in the fact that 

 serpentinous rocks are found in the vicinity of our three 

 silver-lead fields, Mount Zeehan, Mount Dundas, and the 

 Heazlewood. The intrusions of greenstone are met with in 

 several somewhat widely-separated localities. On the road 

 from Strahan to Mount Lyell, from the Queen River Hotel to 

 about a mile past Lynchford, there is a large greenstone 

 mass, which aiso is crossed by the prospectors' track from 

 Lynchford to the Howard Plains nearly to the Queen Eiver. 

 -^s far as I could tell [without analysis and microscopical 

 examination, this rock is exactly the same as the greenstones 

 which are so extensively developed in the central and eastern 

 portions of the colony. I did not notice in it the change to 

 serpentine that is shown by some of the other greenstones I 

 have to speak of. Presumably, it has been intruded through 

 the Silurian sandstones surrounding it, but its effect upon 

 these as to local metamorphism, contortion, fracture, and 

 mineral contents, has yet to be learned. It would be 

 instructive to know if the veins and lodes of quartz traversing 

 the Silurian strata are in any way affected by it, or show any 

 evidence of having been caused by it. 



Round Trial Harbour for about half-a-mile to the north 

 ai id east there are steep hills of serpentinous greenstone, 

 which decomposes to a dark red-brown barren soil, containing 

 niuch magnetic and titanif erous iron ore. It is probably part 

 °* the same set of intrusive basic rocks as the serpentinous 

 gieenstone found nearer Mount Zeehan, extending for about 

 2 miles from above the Agnew Huts nearly to the Comstock 

 line. At the western side this rock has not been greatly 



* tered, and is much like our common greenstones, but 

 owards the east it gets more and more changed to serpentine. 



• e ra zor-back ridge on Handley's section at Mount Dundas 

 s somewhat similar serpentine, only finer for ornamental 



Purposes, and contains asbestos and titanic iron ore. Ser- 

 pentine is also found all along the boundary line of sections 



