52 



characterized by quite an unsually large proportion of zircon 

 inclusions in biotite, each surrounded by a halo. There is 

 often local concentration of these along schistosity directions 

 without any apparent reason. 



Andalusite and cordierite are the only two of the heavier 

 metamorphic minerals found by the author in the schists. 

 Prof. Howchin(38) has noted the occurrence of garnetiferous 

 sands at Kosetta Head and Port Elliot, which are probably 

 derived from the metamorphic rocks of the vicinity. 



(c) Cliff Section at Rosetta Head. — A number of speci- 

 mens were obtained showing the variations to be observed 

 along the track from Victor Harbour to the old jetty at 

 Rosetta Head. As the track cuts across the strike of the 

 rocks there are slight variations of composition and texture. 



No. 1 was obtained about 100 yards past the old barn 

 situated where the coastline bends round to the east, or 

 roughly about 1,200 yards from the contact. It is a very 

 compact rock of a grey colour with a micaceous sheen. Slight 

 schistosity is visible and the laminae are curved, possibly due 

 to the intrusion of a vein of quartz and biotite. Microscopic- 

 ally the rock is an exceedingly fine- textured aggregate, mainly 

 of quartz and biotite with subordinate iron ore. Many of 

 the grains are not greater than '01 mm. in diameter, so that 

 the identification of the colourless constituents is very difficult 

 and the presence or absence of felspar could not be determined. 

 A slightly coarse layer in the rock does show plagioclase with 

 a higher refractive index than Canada Balsam. The rock is 

 distinctly schistose. 



No. 2 is likewise somewhat schistose, of a dull-grey colour, 

 very compact, and with a hardness of 5. A sprinkle of 

 browmish mica flakes serves to reveal the schistosity. In thin 

 section the rock is very fine grained, averaging about "08 mm. 

 Schistosity is distinct, and the following minerals were 

 identified: — Quartz, chlorite, biotite, albite, rutile, and a 

 little iron ore. 



Chlorite is a very pale green, almost colourless, with a 

 faint pleochroism. Rutile is fairly plentiful in little prisms 

 and granules. Biotite flakes up to '5 mm. in length give a 

 pseudoporphyritic character to the rock; they are somewhat 

 bleached. 



The rock might be termed a very fine schistose hornfels. 



No. 3, about 480 yards distant from the contact, shows 

 very different characters from Nos. 1 and 2. It has a kind of 

 pepper-and-salt colour, due to the presence of biotite and 

 chlorite, and a micaceous lustre, and is much roughened by 

 knots. 



(38) Geology of South Australia, p. 45. 



