150 GREAT SERPENTINE BELT OF NEW SOUTH WALES, iv., 



richer in quartz and albite, pass into quartz-keratophyre. Many 

 intermediate rocks have been found. The rarer type of passage 

 is that in which, by decrease in the amount of pyroxene and 

 increase in the iron ore of a spilitic rock, a black slaggy rock is 

 produced, to which the name magnetite-keratophyre may be 

 applied. Far more common, however, is the association of mag- 

 netite-keratophyre with keratophyre propei', quite apart from 

 any passa^ge into the spilite-group. 



The true keratophyre is represented by the sill at the head of 

 Oakenville Creek. It consists(1013) of almost pure albite, not 

 acid oligoclase as stated in the earlier account. The analysis, 

 making the same assumptions as before, shows that the felspar 

 has the composition AbgAnj. There is, in addition, a little 

 magnetite, limonite, chlorite, and carbonates. In some speci- 

 mens there are little rods of haematite, which may be pseudo- 

 morphous after hornblende. (There are little pseudomorphs of 

 this character in the porphyries of the Nundle district.) The 

 texture of the keratophyre is trachytic, but not markedly so, and 

 the laths are of uniform size, being about a fifth of a millimetre 

 in length, with a few small phenocrysts (Plate xxvi., fig, 11). 



Just north of Folly Creek, near the track to Bowling Alley 

 Point, is a slag-like rock(1084) with well marked trachytic habit, 

 consisting of albite, magnetite, and chlorite pseudomorphous after 

 augite. The magnetite is very abundant, and occurs in exceed- 

 ingly minute but well shaped crystals. The felspar is in clear 

 laths and microlites. This is an example of the passage-type 

 between a spilite and a magnetite-keratophyre. It differs from 

 the usual type of the latter rock in being quite massive, with 

 little or no scoriaceous habit. 



The keratophyre-complex by Hyde's Creek yields the most 

 interesting types. The pinkish- white nodular rock to east and 

 west of the magnetite-keratophyre, is made up of small fragments 

 of very trachytic rock, the flow-directions in the several frag- 

 ments lying without any regard to the flow-directions in adjacent 

 fragments(1108). Each fragment is made up almost entirel}^ of 

 albite laths, the larger laths lying in a matrix of exceedingly 

 minute microlites and a little quartz. The felspar is often very 



