166 F. L. StiUivell: 



wavy extinction and is untwinned or simply twinned. In ordi- 

 nary light it is mostly clear and colourless, and where cleavage 

 is present it is found to have a very low angle of extinction. 

 It is mostly allotriomorphic, but in places the crystal outline is 

 partly discernible, and then it shows a tendency to a rhombic 

 outline. Application of the Becke method shows that it has a 

 refractive index lower than that of labradorite. The micro- 

 scopical evidence is therefore in favour of its determination as a 

 soda-orthoclase or anorthoolase, and this conclusion is in perfect 

 concordance with the chemical analysis.- 



The augite occurs as small grains and prisms intimately asso- 

 ciated with the brown glass. Its colour is yellowish-brown, in- 

 dicating a titanium variety. 



Apatite occurs as minute inclusions in the felspar laths, and 

 grains of ilmenite or magnetite occur throughout. Microlites 

 which are opaque, and therefore probably ilmenite or magnetite, 

 occur abundantly throughout the brown glass. Microlites of 

 felspar and augite may, in addition, be seen. 



Besides the above minerals there is present a pale green mineral 

 which is isotropic. It shows in part a banded appearance, and 

 is some form of secondary amorphous silica, probably hyalite. 



The rock may be described as an olivine anorthoclase (?) 

 basalt. 



Tertiary Sedimbntaries. 



These consist of fine sands, hard quartzites and coarse and fine 

 ferruginous grits. Many of the boulders of quartzite contain 

 rounded pebbles of quartz embedded in them. Tlie ferruginous 

 grits often contain nodular concretions of limonite. The quartz- 

 ites and grits occur as a fringe along the sides of the valley 

 underlying the newer basalt. The unconsolidated sands are 

 well exposed in a gully in Section XV., T^llamarine, which drains 

 into the Moonee Ponds Creek. Lower down this same gully the 

 quartzites may be observed. 



Pipe-like concretions of limonite, which look like branches of 

 trees, have been observed in the grits, but these, like those at 

 West Essendon (8), show on examination no trace of plant struc- 

 ture. 



