Petrology of Victorian Granites. 217 



felspar, which is apparently oligoclase, is represented in larger 

 quantity than the monoclinic ; the triclinic crystals have good 

 terminal faces, while the orthoclase rarely has. Among the 

 accessory minerals are zircon and apatite. The order of crystal- 

 lization appears to have been — accessory minerals, mica, oligoclase, 

 orthoclase, and quartz. The latter mineral is free from inclu- 

 sions. This granitite is intrusive into the Upper Silurian Rocks. 



Harkaivay. — A line-grained syenite showing a white felspar, 

 biotite, hornblende, and much quartz. Monoclinic felspar 

 appears under the microscope both in larger crystals and greater 

 quantity than tlie triclinic felspar; the latter has the more 

 perfect crystal edges of the two, and is a frequent inclusion in 

 the monoclinic felspar. This phomenon of inclusion and the 

 manner in which the orthoclase is moulded on the plagioclase 

 show that the latter mineral was the hrst to crystallize. Horn- 

 blende is present in small quantity ; it is somewhat bleached in 

 colour, and is only faintly pleochroic ; the crystals have ill-defined 

 terminal faces. Biotite is often altered to chlorite. A small 

 amount of apatite is present. 



This rock is in many places traversed by tine-grained veins, 

 which weather out from the softer main mass. Under the micro- 

 scope it is seen to be mainly composed of quartz grains, through 

 which are distributed ill-bounded crystals of microcline, a 

 triclinic felspar — probably oligoclase — grains of a monoclinic 

 felspar and a minute quantity of mica. There is no trace of 

 hornblende. The material forming these veins appears to occupy 

 cracks formed in the main mass by contraction under cooling, and 

 to be a later emission from the central magma. Its constitution 

 seems to support the view that when more than one emission 

 takes place from the same central magma, the later emissions are 

 more acid in character than the earlier ones. 



Warlmrtoti, six miles east of township, near tin-mine. — A 

 coarse-grained granite with large pink felspars, blebs of quartz 

 and a small quantity of nuca. Under the microscope it is seen 

 that the prevailing felspar is a somewhat cloudy orthoclase. The 

 triclinic felspar is oligoclase, it occurs as a frequent inclusion in 

 the orthoclase, when it is sometimes bounded by a thin layer of 

 quartz. There are indications in one slide that a partial 

 crystallization of the quartz had accompanied that of the ortho- 

 clase. Apatite is sparingly represented. 



