THE GEOLOGY OF MITTAGONG. SoM 
test for nepheline. No definite result was obtained, the 
small amount of mineral which absorbed the stain being 
very probably a decomposition product. 
No. 3. Locality Top of Mount Jellore. 
(See Plate 26, fig. 2.) 
Texture—Hypautomorphic granular. No base is present, 
but rock consists of a mixture of somewhat rounded 
grains of orthoclase mingled with larger but less 
abundant quartz. Insome parts of the slide the inter- 
stices are filled with a strongly pleochroic hornblende. 
Minerals present (approximate area)— 
Felspar (few small phenocrysts) ... cep Gare 
Quartz ... Sy: we oe ise Bog lO 
Hornblende “ef ei bas Sats hy a 
Felspar is all somewhat kaolinised. The majority have 
the form of short laths and a few are singly twinned. No 
plagioclase is distinguishable. 
Quartz is subordinate in shape, of clear undecomposed 
grains. 
Hornblende has the form of irregular masses with a 
somewhat poikilitic structure. It occurs in bunches sur- 
rounding felspars throughout the section. The colour in 
ordinary light is bluish-green. It shows intense pleochroism 
changing from olive-green to myrtle green, and seems to 
be most closely akin to arfvedsonite. (See Plate 26, fig. 2 
and Analysis I.) 
Order of Consolidation. 
Felspar 
Quartz 
Arfvedsonite 
Name.—This rock is on the borderline between trachytes 
and syenites, and contains too much quartz to be a typical 
trachyte. It seems to be similar to the quartz-syenite of 
