120 



the coloured constituents. Microcline is quite the predomi- 

 nant mineral, in rounded or irregular grains about a milli- 

 metre in diameter. It is characteristically developed and is 

 microperthitically intergrown with albite lamellae. It is 

 quite free from decomposition. Second in order of abund- 

 ance is uralite after diopside. It is actinolite, faintly pleo- 

 chroic, and in irregular grains dusted with epidote. Almost 

 equal in amount to the uralite is plagioclase in irregular 

 grains of composition, Abg An,. Ilmenite is present in small 

 amount, largely changed to titanomorphite, and a few 

 rounded grains of sphene, of a pale-bronze colour and very 

 pleochroic, apiDcar also to be titanomorphite derived from 

 ilmenite, being clouded with reddish- white leucoxene. Quartz 

 with gaseous inclusions occur in small amount inter sertally. 

 Name. — Microcline diopside syenite. The microphotograph 

 (plate iii., fig. 2) is of a section closely similar to this rock. 



608. Locality. — From the eastern vein in Sections 580 

 and 575, of the Hundred of Para Wira. Macroscopically 

 medium-grained ; predominantly composed of white felspar 

 with a smaller amount of pink orthoclase. Large hornblende 

 crystals occur rather fibrous in character, but with a good 

 cleavage. Microsco'pically. — Texture hypidiomorphic granu- 

 lar, grainsize even, about 3 mm. The predominant mineral 

 is an acid oligoclase, closely followed by orthoclase occurring 

 in large irregular grains and showing straining. The chief 

 ferromagnesian mineral is uralite, in large anhedrons, which 

 are green and faintly pleochroic, associated with and some- 

 times including crystals of pale-brown-green ; strongly pleo- 

 chroic hornblende. Titaniferous magnetite also is present in 

 primary grains, and probably secondary magnetite occurs in 

 the cleavages of the hornblende and uralite. Biotite flakes 

 occur in a couple of grains of hornblende as very small 

 patches in the cleavages. Name. — Hornblende diorite ap- 

 proaching monzonite. 



Locality. — Portion of the large eastern extension of the 

 intrusion in Sections 581 and 573, of the Hundred of Para 

 Wirra. Macroscojncally . — The grainsize is unusually large 

 white felspar grains up to 3 mm., with large diopside grains 

 showing fair cleavage '5 mm. in diameter. A little magne- 

 tite is noticeable. Microscopical characters. — Texture hyp- 

 idiomorphic granular, with no sign of marginal crushing of 

 the grains, though the felspar lamellae are occasionally bent 

 and faulted. Plagioclase (Ab, An^) is the predominant min- 

 eral, and a little orthoclase is present as well. The chief col- 

 oured constituent is a pale-green diopside, but primary horn- 

 blende is present in some amount, forming strongly pleochroic 



