174 THE GEOLOGY OF THE CANOBOLAS MOUNTAINS, 



occur, and also some grains of a yellow isotropic mineral with 

 high refractive index, which tend to gather round the brown 

 amphibole. This j^ellow mineral is probably perofskite. 



3. Order of consolidation. 



Rutile 



Kataphorite and 



Cossyrite(?) 



Riebeckite 



PerofskiteC?) 



Anorthoclase — 



(1st generation) 



Do. (later generations) 



Quartz 



Glass 



4. Name : Trachytic Kataphorite-Riebeckite-Comendite. 



5. Magmatic name: Kallerudose (see Analysis vi., p. 191). This 

 magma is common in the Glass House Mountains. 



No.X.583. Quartz-Trachyte. Loc: Canobolas. 



Microscopic Texture : fine-grained, holocrystalline, with an 

 hypidiomorphic granular fabric approaching orthophyric. 



Constituents : felspar, arfvedsonite, segirine-augite, quartz, and 

 eudialyte(?). The felspar consists of corroded, anorthoclase pheno- 

 crysts exhibiting shadowy extinction, and fine sanidine microlites 

 with an extinction of 8°-10°. Some are nephilinitoid, and some 

 prismatic in habit. The amphibole consists of mossy poikilitic 

 aggregates, which exhibit the pleochroism of arfvedsonite (viz., 

 r deep blue-black, b lavender, a pale greenish-yellow), and of 

 ragged grains which approach riebeckite closely in colour and 

 pleochroism, but have a higher extinction-angle (about 10°). The 

 absorption of the typical poikilitic arfvedsonite is t^-h^ti, and 

 the extinction (a : c') = 14°. Skeleton crystals of brown pleochroic 

 cossvrite occur sparingly. Yery minute segirine-augite grains and 

 rods are abundant interstitially. A yellow, feebly pleochroic 

 mineral occurs; it changes from yellow to a faint peach-blossom 

 tint on rotating the stage, and is resolved between crossed nicols 

 into zones, some of which are isotropic, others doubly refracting. 



