BY W. N. BENSON. 693 



darker augite-phenocrysts, and abundant, pale green crystals of 

 plagioclase, 3 mm. in diameter, showing zonary banding very 

 distinctly. This is labradorite. The augite-phenocrysts have 

 passed into peculiar, spherulitic masses of chlorite. The ground- 

 mass is finely crystallised, lathy andesine, with a little epidote 

 and chlorite, and much leucoxene. Some pyrites is present. 

 Occasionally, the rock is very rich in veins and spherules of white 

 prehnite, as in M.B., 64, from the intrusions on the Manilla River 

 at Plumthorpe, 10 miles west of Barraba. 



Possibly there should be classed with this group M.B., 285, a 

 purplish-green rock forming a narrow band in the mudstone one 

 mile west of Eulowrie homestead, on the Horton River. It con- 

 sists of large and small phenocrysts of zoned plagioclase, with 

 pseudomorphs of calcite and chlorite after a pyroxene, possibly 

 hypersthene, though they are not unlike the augite-pseudomorphs 

 in the Blue Knob dolerite. The ground-mass is quite subordinate. 

 It consists of orthophyric plagioclase-crystals, with a little augite 

 and some magnetite, set in a small amount of glassy base. 



(9). Granites, Granodiorites, and Porphyries. — The grouping 

 in order of age, given in Part i., was as under : — 

 (a)Felsites, etc., of the Bingara District. 

 (b)Granodiorites of Nun die and their associated porphyries. 

 (c)Sphene-granites of Moonbi. 

 (d)Tingha granite. 

 (e)Acid granite. 

 (/) Tourmaline-granite. 



(a) An example of this group occurs near the Ruby Hill basalt- 

 neck, south of Bingara. Mr. Pittman describes it as a microcrystal- 

 line quartz-felsite. 



(b) The chief feature of the second group is the immense number 

 and variety of the porphyritic apophyses. As typical of the 

 plutonic members, are described N.T., 384, from the upper end of 

 Duncan's Creek, and N.T., 413, from Mt. Ephraim. The former 

 has a hypidiomorphic, granular texture, and consists of zoned oligo- 

 clase-andesine, a very little orthoclase, abundant quartz showing 



