338 T. G. TAYLOR AND D. MAWSON. 
Olivine.—One large crystal is of a curious annular shape, 
evidently due to corrosion, showing a portion of the dark 
ground mass included within the crystal. 
Order of Consolidation. 
Olivine 
Helspar 
| magnetite 
olivine 
felspar 
Name.—Rock belongs to basalt family. The abundance 
of magnetite both in the base and in layer masses would 
seem to justify the name MAGNETITE BASALT.’ 
Basalts occur in great variety around Mittagong. In 
addition to those described above, mention may be made of 
the following :— 
A basalt from the top of the sandstone hill one and a half 
miles north west of the Gib. A shaft has been sunk 
through this basalt, presumably to prospect for ironstone. 
In thin sections the basalt is characterised by large clear 
augites and felspars, olivine is abundant. The augites 
have a peculiar smoky colour. 
A basalt from a small knob close to the Vice Regal 
residence at Sutton Forest, some miles south of Mittagong 
may be mentioned here. The small granular augites in 
thin sections are seen to be enclosed in a large mass of 
felspar showing poikilitic structure. This is rather rare 
in felspars. 
Basalts presenting ordinary features can be obtained 
from Jellore Creek, Nattai River near the coal adits, Wood- 
lands Hstate, and the knob over the north end of the Gib - 
Railway Tunnel. 
1 N.B.—The above somewhat remarkable basalt lies outside the area 
of our map and was found during a walk to the abandoned diamond 
flelds on the Nepean River. 
_ - so 
