136 



mass of the rock is a fine-grained mass of lepidoblastic quartz: 

 and biotite, largely obscured by bands of sericite. Ilmenite 

 is present in large grains, partly leucoxenized. It generally 

 occurs included in a sericitic band. In these bands are often 

 flakes of dark-green biotite, dusted with secondary titanifer- 

 ous magnetite. 



A type of rock quite different from these is found in 

 the Little Para just below Inglewood. It is a dull-green in 

 colour and silky or greasy to the touch. It is chiefly com- 

 posed of pale-yellow-green weakly pleochroic actinolite, whose 

 somewhat feathery arrangement makes the structure of the 

 rock approximate to the nematoblastic structiire defined by 

 Grubenmann. Fairly idiomorphic cross sections of the amplii- 

 bole occur, however. The groundmass of the rock is made 

 up of fine-grained granoblastic quartz, with a little poikilo- 

 blastic orthoclase and an occasional idioblast of albite. The 

 groundmass is quite subordinate, however, to the actinolite. 

 The feature of the rock, however, is the occurrence of a large 

 amount of calcite, either in single grains among the actino- 

 lite or aggregated into bunches. It is generally granular. 

 There seems little doubt that the calcite is primary, and that 

 the rock represents a very impure limestone that has been 

 altered probably in the lower part of the upper or metamor- 

 phism zone, as limited by Grubenmann. The conditions 

 there were inducive of a crystalloblastic other than a kata- 

 blastic structure. It should be mentioned that magnetite 

 also occurs distributed through the rock in roughly par- 

 allel bands. 



Just in front of the Houghton schoolhouse is a pale- 

 green schist which is composed mac roscojnccdly of larger 

 grains of quartz, a few large muscovite flakes, some irregular 

 brown grains, and some black wdth metallic lustre, all set 

 in a very pale-green sericitic groundmass. Microscojncally 

 the rock contains large irregular highly-strained quartz grains 

 in a groundmass of granoblastic quartz. Large bent mica 

 plates occur, and brown to purple tourmaline in irregular 

 gi'ains. Magnetite is present in some amount. Covering 

 most of the quartz of the aggregate is an aggregate of very 

 small flakes of muscovite in radiate or feathery groups. An 

 occasional grain of rutile occurs. This does not seem to be- 

 derivable from the same sediment as the Houghton, Barossa, 

 and Yankalilla schists, but it is doubtless a member of the 

 same Pre-Cambrian series. The tourmaline is certainly 

 secondary. 



Another type of rock occurs just opposite the Inglewood 

 Hotel. It is a hsematite schist, forming in a small area in 

 the intrusive rock. Microscopically its schistose texture is 



