BY H. I. JENSEN. 869 



Another specimen of the andesite formation, macroscoi^ically 

 of green colour and moderately tine texture, consisted of a pale 

 hornblende (like edenite), a greenish glass, some magnetite, 

 quartz, orthoclase, plagioclase and a little biotite. The pale green 

 hornblende was the chief constituent. 



{Hi.) Mt. Jlelhim Basalts. — The basalts of Mt. Mellum bear 

 close resemblance to the amygdaloidal basalts of Tambourine 

 Mountain, described by Mr. Rands. 



Mr. Rands describes the Tambourine basalts as amygdaloidal 

 on the upper surface, generally full of olivine phenocrysts; and 

 occasionally columnar, the columns being often '20 feet in length, 

 and hexagonal in section. 



The Mellum rock is in part vesicular, in part columnar. It 

 contains large phenocrysts of olivine, plagioclase and black 

 augite. The vesicular basalt occurs at the lowest and highest 

 levels of the basalt. The rock is very rich in olivine; a dark red 

 olivine (iron olivine, fayalite) is also present, and has taken the 

 place of magnetite. Fayalite occurs sometimes as a nucleus to 

 ordinary olivine, and was evidently the first mineral to crystallise. 

 Ilmenite is present in tabular crystals, sometimes passing into 

 leucoxene. The auyite crystallised simultaneously with the 

 plagioclase^ the two minerals being intergrown. The augite seems 

 to be titaniferous. The plagioclase agrees well in properties 

 with andesine. 



(c) Other Rocks. — At the base of the Round Mountain, on 

 the fS.E. side, there is an outcrop of aplite, which probably marks 

 the position of an outlier of palaeozoic igneous rock. This aplite 

 consists of quartz, orthoclase and plagioclase. Hand specimens 

 are brick-red, and look like metamorphic sandstone. The mineral 

 staining of the Round Mountain trachyte is probably connected 

 in some way with this aplitic mass. 



On the western side of the D'Aguilar Range at Butler's Creek, 

 there are dykes of legf-.rine syenite traversing the granite. 

 Recently, through the kindness of Professor David, I have 

 had an opportunity of looking over a large number of specimens 



