458 PROCEEDINGS OF SECTION E. 



Mica. — Principally well developed. Biotites as irreojular plates 

 Avith parallel striae along the vertical axis ; flakes of muscovile 

 also occur. 



Apatite. — Numerous hexagonal and spindle-shaped forms occur 

 as inclusions in the biotites. 



Zircon. — Bright pleochroic grains are seen along the margins of 

 some of the biotites. 



This granite is prized as an ornamental building stone. Its 

 specific gravity is higher than any of the Victorian granites, and 

 it takes a high polish. The grits and sandstones which form the 

 western margin of the Mesozoic area at Griffith's Point are largely 

 made up of the detritus of this yranite. I have traced the 

 altered biotites and felspars through various stages and altera- 

 tions from the normal state in which they occur in the granite 

 to these clastic rocks. The mica has its laminae replaced by 

 lenticular-shaped deposits of calcite, and the orthoclase felspars 

 are much kaolinised in the latter rocks. From its geological 

 relations to the Silurian sediments to the north-west I refer this 

 granite to the Devonian (Lower) Period. 



Wilson's pf.omontory. 



The whole of the promontory is made up of a very coarse grey 

 granite ; at one locality, however, it is pink and white. The pre- 

 vailing structure is somewhat i)orphyritic, there being large 

 irregular perthite and orthoclase crystals with subordinate mica, 

 and amorphous quartz. Mr. Murray in his descriptions refers to 

 its structure on the Corner Inlet coast as containing veins of 

 felspar, with enclosed quartz veins surrounding masses of fine 

 granite, composed principally of quartz and felspar with a little 

 mica, and also as containing (in places) irregular veins of tour- 

 maline with white nrica, and nearly white granite containing very 

 little mica. Near Yanakii it contains small garnets, zircons, 

 green and blue sapphires, topaz, and small almandine rubies. 



A slice prepared from the rock at Yanakii gave me the follow- 

 ing :— 



Quartz. — Allotriomorphie grains of quartz, in places containing 

 swarms and streaks of fluid inclusions. 



Felspar. — Large perthites and orthoclase. Idiomorphic plagio- 

 clase felspars occur within the areas occupied by the orthoclase 

 or microperthite. In some of the glassy neutral-tinted felspars 

 cloudy or dusty aggregations of kaolinite are seen. There are 

 also some beautiful fine sericite aggregations. 



Mica. — Two kinds of mica occur. Biotites in lath-shaped 

 sections, with frayed edges and irridescent flakes of muscovite, 

 and also in basal sections with inclusions. 



Tourmaline. — Small crystals occur as inclusions in the quartz. 



Zircon. — Small crystals in the larger felspars. 



AjKitite. — As inclusions in the biotites. 



