220 Proceedings of ilte Royal Society of Victoria. 



marked pleocliroism are scattered through the slide. A some- 

 what fibrous biotite, often bent and contorted, is sparingly 

 distributed. Apatite occurs in prisms and grains, it is a frequent 

 inclusion in hornblende and biotite. 



Droniana. — Coast near township. — The main rock mass is 

 here too weathered to furnish satisfactory slides. It is, liowever, 

 penetrated by veins and contains ovoid patches very similar in 

 appearance to those occurring at Mount Martha and previously 

 described. Under the microscope it is seen that in the basic 

 secretion hornblende is the prevailing mineral, there is a fair 

 amount of mica, and both monoclinic and triclinic felspars appear. 

 Sphene and apatite both occur and there are traces of quartz. 

 As at Mount Martha, the veins are poor in mica and entirely 

 without hornblende. 



Cobiaigra High Plaifis. — A medium-grained granite with a 

 pink felspar, bottle green quartz and biotite in small clusters. 

 In this rock the prevailing felspar is a monoclinic which contains 

 many rounded fragments of triclinic felspar. Both felspars are 

 much altered and clouded. A striking feature of the rock is the 

 abundance of sphene and tiie occurrence of ilmenite in character- 

 istic cross-hatched sections. Apatite is also present. 



Watts River. — Aqueduct, near Healesville. — A medium-grained 

 granitite showing white felspar, greenish quartz and biotite. 

 Careful examination of the slide shows that the triclinic felspar 

 occurs more largely than the monoclinic, it has better crystal 

 boundaries and has suffered less alteration. Measurements of 

 the triclinic felspar give a maximum extinction angle of 16°, thus 

 leavino- it in doubt whether the felspar is an albite or oligoclase- 

 andesine. Biotite is well represented, it is frequently altered to 

 chlorite. Apatite is present. Calcite and muscovite appear as 

 secondary products. 



Little Snowy Creek. — Above Tallandoon, near Tallangatta, 

 Mitta Mitta River. — A coarse-grained greisen with cassiterite. 

 The rock is almost entirely composed of quartz and muscovite. 

 Sphene is present in fair quantity. The quartz grains are 

 charged with opaque dust which is arranged along intersecting 

 lines and curves. 



Mount Hotham to Victoria River, Cobutigra. — A somewhat 

 fine-grained granite rich in quartz and biotite with white felspar. 



