212 Proceedings of the Royal Society of Victoria. 



3. A basalt containing much glass, triclinic felspar — showing 

 both albite and pericline twinning — augite and magnetite. The 

 felspar occurs both as plienocrysts and niicroliths : the augite is 

 present only in grains. 



4. A coarse-grained holocrystalline olivine basalt rich in tri- 

 clinic felspar ; augite occurs both as grains and phenocrysts, the 

 latter being sometimes twinned. The slide shows traces of 

 ophitic structure; olivine has been almost entirely serpentinized ; 

 magnetite is also present. 



o. A volcanic ash with schistose structure. Angular 

 fragments of quartz, plagioclase felspar and augite can be seen, 

 but alteration of the rock renders further determination 

 impossible. 



6. A fine grained rock of bluish-black colour, in which felspar 

 and hornblende can be seen. The base is composed of crystals 

 of nepheline, lath-shaped felspars and grains of augite. Sanidine 

 occurs in pellucid crystals of tabular habit and showing Cai'lsbad 

 twinning. Alteration of the crystal has taken place either by 

 the deposition of opaque specks along the partmgs, or by infil- 

 tration into eracks of silicious matter with high polarisation tints. 

 There is much hornblende, but it has been a good deal modified. 

 Around the larger crystals a deep coloured zonal border has been 

 formed, leaving a strongly pleochi-oic interior. The smaller 

 crystals have become entirely opaque by the same resorbing 

 action of the magma as that which produced the zonal border in 

 the larger crystals. At the same time, the alteration of the 

 hornblende has been accompanied by the formation of minute 

 iriegular grains of augite which surround the hornblende crystals 

 and give them a frayed appearance. Augite also occurs as 

 phenocrysts, but with ill-defined crystal edges. Nepheline is well 

 represented in the slide in microscopic crystals, giving quadratic 

 and hexagonal sections. Apatite occurs in rather long prismatic 

 ci ystals, and is frequently seen as an inclusion in the hornblende. 

 There is some sphene present and epidote occurs as an alteration 

 product of hornblende. The rock should be classed as a horn- 

 blende phonolite. 



7. A somewhat decomposed rock of light grey colour, in which 

 felspar and hornblende are visible. There is some glass present 

 in the base, also magnetite, augite grains andmicroliths of felspar. 



