Petrology of Victorian Granites. 221 



It is with some diffidence I class this as a granite, as owing to 

 the decomposition of the slide it is difficult to determine whether 

 the monoclinic felspar or the triclinic felspar is the preponderat- 

 ing one. Biotite is somewhat bleached and contains minute 

 zircons. Quartz is free from inclusions. Apatite is sparingly 

 represented. 



For the last four specimens described I am indebted to Mr. A. 

 E. Kitson, F.G.S., of the Mines Department. 



Yackandandah. — An account of the field relations of the 

 Yackandandah and Beechworth granitic areas is given in 

 Progress Report, No. 2, of the Department of Mines, pp. 75, etc. 

 The specimens sliced from this locality were all taken from the 

 bed of the creek about a mile below the township. Though the 

 quarries near the township used for building purposes have only 

 been closed for about 10 years it was impossible to find there any 

 specimens which weathering had not rendered quite unfit for 

 slicing. The rock is fairly constant in apjDearance over consider- 

 able areas near the township. Large milk-white crystals of 

 felspar embedded in a matrix of quartz and biotite is the 

 characteristic form, the texture is for the most part coarse. 

 Close inspection shows that mica is a frequent inclusion in the 

 felspar. Scattered through the main mass are frequent patches 

 of dark closed-grained material which is harder and more 

 difficult to fracture tlian the surrounding rock. These patches 

 are of small dimensions and the line of demarcation between 

 them and the surrounding rock is well marked. Biotite, cjuartz 

 and triclinic felspar can be detected in them by the naked eye. 



The main rock mass at Yackandandah is an interesting 

 example of the occurrence within a short distance of each other 

 of both granite and granitite. In some slides the monoclinic, in 

 others the triclinic, felspar is the leading one. The triclinic 

 felspar is an acid oligoclase with a maximum extinction angle 

 measured from the twin line of about 10°. It occurs in two 

 generations, being found not only as an inclusion in the mono- 

 clinic variety but also in the triclinic. There is a small amount 

 of microcline present in the rock. Quartz and biotite are normal. 

 Sphene and apatite occur in most of the slides. 



The basic secretions under the microscope show a crystalline- 

 granular structure in which biotite and mica are the prevailing 



