340 T, G. TAYLOR AND D. MAWSON. 
Name.—Rock evidently belongs to ultrabasic group. | 
Since some felspar is present it belongs to the picrites. 
From the size and abundance of the augite crystals it may 
be termed AUGITE PICRITE. 
A brief description of the four microphotographs (Plate 
26) is appended :— 
Figure 1—Syenite from “‘the Gib.”’ (The darker variety 
from Saunder’s Quarry). This photograph shows the wavy 
appearance of the felspars due to kaolinisation. The opaque 
masses are chiefly ilmenite and magnetite, while the dark 
powdery material results from decomposition of the original 
ferro-magnesian mineral (probably hornblende). 
Figure 2—Quartz trachyte forming summit of Mount 
Jellore. The dark material is the hornblende allied to 
arfvedsonite. The transparent masses are quartz. The 
remainder is chiefly felspar. 
Figure 3—Hssexite from Jellore Creek, showing long 
opaque ragged ilmenites, broad felspar laths and irregular 
darker masses of augite. 
Figure 4—Augite picrite from Jellore Creek. Augite 
is characterised by the strong cleavage. The serpentine 
shows as dark cloudy masses. Felspar constitutes the 
colourless material. An exceptionally large mass of mag- 
netite occupies one side of the photograph. 
Reference list of rock sections described :—1. Syenite, 
Bowral; 2. Aegirine trachyte, Mount Jellore; 3. Arfived- 
sonite quartz trachyte, Mount Jellore; 4. Trachyte tuff, 
near the west slope of the Gib; 5. Dolerite, Mittagong ; 
6. Ilmenite essexite, Jellore Creek; 7. Olivine basalt, 
Mittagong; 8. Magnetite basalt, McGuire’s Creek; 9. 
Augite picrite, Jellore. 
. 
A stereogram of the Mittagong District will be found at 
the end of this paper. 
