Albite Syenite. — The porpliyritic granite has associated 

 with it a mass of albite mica syenite. This is a coarse-grained 

 rock, typically containing large phenocrysts, up to 2 in. long 

 by about IJ in. broad, and simply twinned. The remainder 

 of the rock is composed, megascopically, of smaller felspars, 

 with a varying amount of silvery-grey chloritic mica. The 

 porphyritic character is sometimes lacking, and in these cir- 

 cumstances mica is usually very abundant. The white colour 

 and the absence of megascopic quartz clearly differentiate 

 this rock in the field from the porphyritic granite. 



Probably owing to the presence of chlorite the rock is 

 extremely tough, and good specimens are rather difficult to 

 procare. 



On the northern side of the headland, near the old wharf, 

 the syenite is in contact with the invaded schists, which it 

 has altered considerably and into which it has thrust long 

 tongues of non-porphyritic material, as well as numbers 

 of veins, large and small, composed of quartz and mica. 



Following the shore-line round to the east and south one 

 finds the syenite continuing for some distance, but it is soon 

 replaced by granite, the boundary of the two rocks sloping 

 upward towards the south. 



On the southern side of Rosetta Head the syenite is again 

 seen, and for a considerable distance on the landward side it 

 is the rock in contact with the schists. In spite of all the 

 exposures, however, a junction showing clearly the relations of 

 granite and syenite was not found. 



Enclosures of the country rock, sometimes several yards 

 in diameter, are found in both the syenite and the granite, 

 and occasional pipes of potash aplite cut through the coarser- 

 grained rocks. 



Uralitic Dolerlte. — A number of altered basic dykes are 

 to be seen in the neighbourhood of Rosetta Head. One of 

 these runs in an approximately meridional direction behind 

 the headland among the schists ; another, following the strike 

 of the schists, is encountered on the shore between the head- 

 land and King Point, while a third, not more than 3 ft. wide, 

 cuts the granite and can be seen outcropping on the top of 

 the headland somewhat on the southern side. This is trace- 

 able through the plutonic rock for a distance of about 40 

 yards. 



Prof. Howchin has recorded the existence of numerous 

 other similar dykes at various points inland from Rosetta 

 Head, and the present writer has observed one exactly com- 

 parable with those at Rosetta Head, about 6 miles up the 

 valley of the Inman. 



