370 C. A. SUSSMILCH AND W. G. STONE. 



mineral was detected. The augite when present is associ- 

 ated with its alteration products, chlorite mainly, calcite, 

 epidote and iron ores. A few small phenocrysts of horn- 

 blende were noticed. 



Iron ores (in part secondary). Both ilmenite and mag- 

 netite are present mainly in groups of grains and crystals 

 associated with chlorite, where it represents segregations 

 during the alteration of the ferro-magnesian minerals. It is 

 also scattered sparingly through the groundmass. Ilmenite 

 appears to be the most plentiful, but as they generally occur 

 together, it is often impossible to distinguish between them. 

 Ilmenite frequently shows a typical skeleton form of growth 

 arranged in three parallel groups which cut each other at 

 60° in cross section. In some instances it is altered to 

 leucoxene. 



Apatite occurs in the matrix as small prisms and needle- 

 like crystals. It is also rather plentifully included in the 

 chlorite patches and less sparingly in the felspars. It is 

 more abundant here than in the other types of rock 

 described. 



The secondary minerals are chlorite, calcite, kaolin, 

 sericitic material and epidote. 



Chlorite is the most abundant of these products and occurs 

 in patches up to 5 mm. in size. It is present as an alter- 

 ation product of the phenocrysts and the groundmass. It 

 is undoubtedly the principal alteration product of a ferro- 

 magnesian mineral, and from its association in x 889 with 

 augite, it is probably in large part derived from that 

 mineral. It is of a fibrous nature and pale green colour 

 and generally faintly pleochroic. Between X nicols it 

 shows a deep ultramarine blue, and in some instances is 

 almost isotropic. 



Calcite occurs rather plentifully, and according to the 

 analysis occupies about two per cent, of the rock. It is an 



