NEPHEL1NE-BEARING ROCKS. 183 



appearance is shown by fig. 4, Plate 6. It is seen to con- 

 tain large, perfectly developed, phenocrysts of purple augite 

 which have often an exterior zone full of minute inclusions 

 of ilmenite, olivine, and scraps of plagioclase, giving a very 

 pitted appearance. Usually the colour changes from strong 

 purplish pink on the inner portion of this zone, to greenish- 

 grey on the outer portion. These phenocrysts are up to 

 three millimetres in diameter. There are numerous smaller 

 phenocrysts of olivine. The ground-mass consists of short 

 felspar laths, many of which are sanidine, and abundant 

 hexagonal prisms of nepheline. A good deal of this has 

 been changed into natrolite. As this rock has a much 

 finer grain than any of the others and a far more volcanic 

 habit, it may be termed a nepheline basanite. The small 

 amount of plagioclase present prevents it from falling 

 directly under the nepheline basalts, using the term in its 

 strict sense. 



A mile south-east of Goonoo Goonoo Station and about 

 twenty miles north-west of Nundle is a small knoll, Ourra- 

 jong Hill. On a very hasty examination it appeared to be 

 a neck about ten yards (from memory) in diameter com- 

 posed of a coarse grained rock of granite texture with dark 

 purple black pyroxene. On section, this proves to be also 

 closely related to the rocks above described. It is a 

 remarkably fresh rock, and contains large purple augites, 

 clear olivines, large labradorite tabulae, with a fair amount 

 of interstitial orthoclase. Numerous small crystals of 

 ilmenite are present, often surrounded by bright red-brown 

 pleochroic biotite. Apatite prisms are well developed. 

 The rock is best termed an essexite. 



Here attention should be drawn to the similarity, several 

 times remarked upon by Dr. Jensen, 1 between these rocks 

 and the essexites, described by him, which occur as rolled 



1 Proc. Linn. Soc. N.S. Wales, Vol. xxxn, p. 883, 1907. 



