BY W. N. BENSON. 599 



pyroelastic rocks. The largest development is in the complex on 

 Portion 175, Nemingha. They generally contain some quartz. 

 Two types may be specially noted. Specimen 1140 resembles the 

 rocks from Pipeclay Gully, near Bowling Alley Point(l7). It is 

 vesicular, with phenocrysts of albite, in a base of finer laths of 

 felspar, and a small amount of quartz with chalcedonic margins. 

 Chalcedony also occurs surrounding the grains of quartz. It 

 is probably intermediate in composition between the porphyritic 

 magnetite-keratophyres and the spilites. The first-named are the 

 more coarsely crystalline. Their large phenocrysts are all albite, or 

 are partly replaced by calcite, and a mosaic of minute prisms of 

 albite ; which certainly suggests the secondary nature of the albite. 

 They are also dusted with other secondary material. There are, in 

 addition, large octagonal areas of calcite and chlorite, which doubt- 

 less represent former phenocrysts of augite. A few of these have 

 inclusions of felspar. The base consists of minute laths of acid 

 plagioelase, chlorite, and magnetite, the latter occurring abun- 

 dantly interstitially, and especially segregated about certain lines, 

 as in 1148, and about the calcite-filled vesicles. Specimen 1361 dif- 

 fers from the others in the finer grain size, and in the absence of 

 phenocrysts of augite, and also in the presence of a large amount 

 of black inclusions in the margins of the felspar-crystals, which 

 inclusions, however, do not seem to be of primary origin, but to 

 have been introduced from the magnetitic matrix, and lie in the 

 cleavage-traces of the felspar, and in other definite directions in 

 the crystals that are not marked by any noticeable cleavage. These 

 two rocks also afford evidence of the pneumatolytic introduction 

 of magnetite, in the later stages of their consolidation. 



Magnetite-keratophyre also occurs in Portion 110, Nemingha, in 

 the southern extension of the East Gap Hill zone, but as it has 

 some f ragmen tal characters, it is discussed below. 



Some quartz-keratophyres remain for consideration. One of 

 these (1142) occurs in Portion 138, adjacent to the magnetite- 

 keratophyre of Portion 110. It is porphyritic, with phenocrysts 

 of andesine which fill the numerous vesicles. Dusty haematite is 



