24 on hauyne-trachyte and allied rocks. 



Conclusion. 



^Ye liave abstained from refeiTin<? to several additional 

 minor f^arieties of trachytic rock which we have collected, 

 and which differ slightly from the foregoing, but their 

 minute description in this connection would serve no 

 practical purj^ose, and we doul)t not the discovery of 

 further types will reward the diligent collector. The 

 results of our enquirj^ may be conveniently summarised 

 as follows : — 



1. All round the arm of the Huon, known as Port 

 Cygnet, there is an extensive development of porphyritic 

 rocks, which are phonolitic or soda-trachytes containing 

 haliyne, aegirine, analcime, and cataphoritic hornblende. 

 Some of these furnish the finest examples of orthoclase 

 felspar crystals to be found in the island. 



2. The trachytic area extends to Little Oyster Cove on 

 the N.E., to the N. of Lovett as far as Sugar Loaf Hill, to 

 the S. of Lovett as far as Lymington and the Huon, but 

 requires further exploration bej^ond these limits. 



3. The trachytes are lava sheets contemporaneous with 

 Permo-Carboniferous sandstones and mudstones. 



4. Associated with these trachytic lavas and their tuffs 

 are allied plutonic and dyke rocks, also of a sodic nature ; 

 viz., alkali-syenite (containing elaeolite) and haiiyne- 

 aplite. 



5. There is an interesting development of melanite- 

 garnet in the trachytes and syenite. This garnet seems to 

 run through the whole series, and is a constituent of the 

 auriferous sands of the district. 



G. The dark green rock of the locality described in the 

 older literature as " metamorphic," and looking such to the 

 naked eye, is shown by the microscope to be segirine- 

 trachyte, full of minute acicular crystals of the green soda 

 pyroxene aegirine. 



7. Gold has been found at Lovett, Lymington, and Little 

 Oyster Cove, mostly alluvial, a minute quantity in situ. 

 It is highly probable that the alluvial gold has been 

 derived from the trachyte, disseminated therein in small 

 quantities. The few quartz veins in the trachyte do not 

 seem to have collected this gold to any special extent, 

 though what gold has been found in the matrix has 

 occurred in their neighbourhood. The quartz is so closely 

 associated with, and Imnded with, trachyte that the assay 

 results are inconclusive. Appearances are against these 

 quartz veins being true lodes. 



8. This highly interesting, though small, peculiar petro- 

 graphical province is a purely local one, confined, so far as 



