On the Occurrence of Trachyte in Victorm. 93 



classed as"sanicline and olivine rocks." That among the rocks 

 so named by Mr. Dennant trachyte occurs was pointed out by 

 the present author in a paper on " The Glacial Beds of Toolleen, 

 Coleraine and Wanda Dale," read at tlie Sydney meeting of the 

 A.A.A.S.. 1898, and the boundai-ies of the trachyte area in the 

 immediate vicinity of Coleraine are there given. 



The object of the present paper is to briefly record* the occur- 

 rence of trachyte at Macedon, Mount Diogenes (the Camel's 

 Hump), Dryden's Mount (the Hanging Rock) and Brock's 

 Monument, and to make a few observations concerning the 

 trachyte of the Coleraine district. The igneous rocks of the 

 Macedon area are classed in the Quarter Sheet Map No. 6 of the 

 Geol. Survey as "Trap or Hypogene;" the notes attached recog- 

 nise the variety of igneous rock there displayed but no definite 

 determination of the different rocks and their boundaries is 

 given. An account of the great variety of rock to be found in 

 the Macedon Range may be gathered from Murray's "Geology 

 and Physical Geography of Victoria," page 27. 



The first specimen of trachyte which came into my hands was 

 given to me in February, 1895, by Mr. Graham Officer, B.Sc. It 

 was taken from a small quarry near the waterfall on Turritable 

 Creek, to the south-west of the township of Macedon. I visited 

 the Macedon district in September, 1897, and on subsequent occa- 

 sions, and collected specimens of trachyte between the township 

 and Mount Diogenes, at Mount Diogenes and at Dryden's Mount. 

 My specimens from Brock's Monument I owe to the kindness of 

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



Totvtiship of Macedoii. — Two types of trachyte occur in the 

 township. The first one to be described may be traced at inter- 

 vals from the quarry previously mentioned to the summit of 

 Mount Diogenes. It appears probable that the spur on which 

 the township is built may consist entirely of trachyte of this 

 type. In appearance it is a light coloured rock, of granular 

 texture, and contains numerous pink and flesh-coloured crystals 

 of felspar. Under the microscope the base is seen to resolve 

 itself into a mass of felspar microliths, showing marked flow 

 structure, and minute grains of mica and some opaque material 

 which may be mica presenting the phenomenon of absorption. 

 Neither hornblende nor augite can be definitely traced in the 



