BY THE REV. J. MILNE CURRAN. 191 



b. Volcanic Basic Rocks. 

 Basalt. — An intimate dark blue or black compound of augite, 

 labradorite and olivine, with some glassy matter. Magnetite and 

 ilmenite are generally present as well. The Bathurst basalt is 

 micro-porphyritic in structure, and, according to Mohl's classifica- 

 tion, our rock is a plagioclase basalt. Boricky would call 

 it a felspar-basalt. Rosenbusch makes basalt include all neo- 

 volcanic rocks of basic composition, which essentially contain 

 plagioclase and augite. Olivine, this author does not consider as 

 an essential constituent. As regards structure, this basalt falls 

 under Division 4 in Rosenbusch's classification, and is, therefore, 

 termed hypo-crystalline porphyritic* 



vii. Sedimentary Rocks. 

 Argillaceous Bocks. 



1. Clays. — Composed of hydrous silicate of alumina. The 

 Bathurst clays contain mixtures of sand and iron oxides in various 

 proportions. 



2. Slate. — Indurated clay, sometimes fissile in planes forming 

 an angle with the bedding, but more often fissile in the direction 

 of the bedding. 



Arenaceous Group, 



1. Sand. — Chemical composition, silica. Mineral components, 

 quartz or flint, Beds of sand are common in many of the more 

 recent formations. 



2. Sandstone. — The shingle of the drifts consists of siliceous 

 sandstones to a very great extent ; pure quartz and felspar 

 pebbles, however, predominate. 



3 Conglomerates. — This rock consists of rounded pebbles of 

 quartz, sandstone, slate and jasperoid rock, cemented either by 

 siliceous or ferruginous matter. As stated on p. 181, we have two 

 conglomerates, similar in composition but different in age, near 

 Bathurst. 



* Rosenbusch, Mikroskopische Physiographie der Massigen Gesteine, p. 

 728 ; Zweite Auflage. 

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