THE GEOLOGY OF MITTAGONG. 345 
The minerals orthoclase, nephelite, and diopside appear- 
ing in the norm are absent in the rock. In order to form 
the mode they would have to be molecularly re-arranged 
to the production of pyroxene. 
Classification.—Class III., Order 5, Rang 4, Subrang 3. 
Magmatic name.—Auvergnose. 
V1. Picrite.—This rock was obtained from Jellore Creek 
at the spot indicated on the map. The specific gravities 
of a number of fragments of the rock taken from this out- 
crop show that the specimen analysed is not so basic as 
some of the other specimens, but is of fair average com- 
position. The rock was in an advanced state of serpenti- 
nisation which accounts for the large amount of combined 
water. 
Composition of the ‘‘ norm ’’:— 
Orthoclase ... 3°34 Pyrite... ane "36% 
Albite ... AA OO Apatite pudt hi ale Sa 
Anorthite ... 27°52 Chromite re *24 
Hypersthene... 26°58 Carbon dioxide "40 
Olivine ae OO Water ... th a0 
Masnetite .... 9°51 —— 
Corundum ... Ti 99°60% 
Ilmenite al es ——— 
The norm differs from the mode in the rearrangement of 
its orthoclase, and hypersthene molecules to form augite 
and olivine of the rock. 
Classification.—Class III., Order 5, Rang 4, Subrang 3. 
Magmatic name.—Auvergnose. 
VI. AGE. 
It is unfortunate that in the eastern portion of New 
South Wales, there are no well developed sedimentary . 
deposits of later date than the Trias. The area occupied 
by the Bue Mountains would appear to have been a land 
suriace since that period. Hence it isa matter of extreme 
W—Oct.7, 1903, 
