Petrology of Victorian Granites. 223 



described from the quarry behind the Beechworth Jail. Under 

 the microscope it appears to be somewhat richer in quartz, the 

 relative proportions of the felspars present is about the same, 

 the triclinic felspar occurs as an inclusion in the monoclinic, it 

 has undergone too much alteration to admit of any determination 

 of its character. 



Gabo Island. — My specimens from this locality are due to 

 Professor David, of Sydney University, and to Messrs. Chambers 

 and Clutten, Melbourne. This i-ock has been described in 

 Selwyn's Catalogue of Rock Specimens and Mineral in the 

 National Museum (1868) as a syenitic granite, consisting of red 

 felspar, quartz and hornblende. This description appears to 

 have been copied by Murray in his Geology and Physical Geo- 

 graphy of Victoria (1887), and in the Catalogue of the Rocks of 

 Victoria, in the Technological and Industrial Museum, Melbourne 

 (1894), similar language is employed of this rock. The specimens 

 obtained by me from Professor David did not satisfy this descrip- 

 tion, as biotite was evidently a constituent while hornblende was 

 not. Under the microscope the sections showed much alteration, 

 the felspars being very clouded, while the biotite was largely 

 altered to epidote. In some cases magnetite had separated out 

 in grains from the mica, with the result that the mica had a 

 somewhat bleached appearance, while the intensity of its pleo- 

 chroism was reduced. In addition to the epidote associated with 

 biotite were other clusters of epidote grains ; it is possible that 

 this epidote occurs as an alteration product of hornblende. If 

 such is the case hornblende was originally present in the rock 

 only in small quantity. The monoclinic felspar is the predomi- 

 nant one. Quartz is fairly free from inclusions. Apatite is in 

 considerable quantity, and there are traces of zircons. The 

 specimens obtained from Messrs. Chambers and Clutten 

 approximate in appearance the rock described by Selwyn, 

 but biotite is present in addition to hornblende. In the thin 

 section green hornblende shows moderate pleochroism ; prismatic 

 sections are wanting in tei'minal faces, good cross sections with 

 characteristic cleavages occur. There is some alteration to 

 epidote visible in both the hornblende and the biotite. As 

 regards the felspars, quartz and accessory minerals, this rock is 

 very similar to the one previously described. This variation in 



