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(quartziferous) variety of both the red hornblende syenite 

 and the augite syenite or laurvikite. It is medium grained, 

 of a dark red colour, in places assuming a distinct greenish 

 tinge. It is typically developed in the vicinity of Red 

 Sucker. The feldspar is a cryptoperthitic growth of 

 orthoclase and albite. Green hornblende, often much 

 fractured and decomposed, is the prevailing coloured 

 constituent. Occasionally there is a very little biotite. 

 Quartz occurs in very small amount, both free and gra- 

 phically intergrown with the feldspar. Magnetite, resulting 

 from the decomposition of the hornblende, is usually 

 abundant. Apatite, fluorite, pyrite, and secondary calcite, 

 the accessory minerals, are sparingly represented. 



Red hornblende-syenite. — The red hornblende syenite 

 is perhaps the most important of the subdivisions mentioned 

 for, from the field work so far accomplished, it seems to 

 cover the largest area. The deep red colour of the very 

 abundant feldspar, in contrast with the dark green of 

 the greatly subordinate hornblende, gives the rock a 

 pleasing and conspicuous appearance. It is usually inti- 

 mately associated with the darker coloured augite syenite, 

 into which it differentiates by insensible gradations. This 

 scarcely perceptible transition is well illustrated by expos- 

 ures north of Peninsula harbour and along the railway 

 between Coldwell and Middleton. Pegmatitic phases, 

 in comparatively narrow dyke-like forms, intersect the 

 associated rocks and are present in the midst of the parent 

 plutonic mass. The rock is composed mainly of feldspar 

 (orthoclase and microperthite) and hornbelnde. This 

 hornblende, which is a variety closely related to barke- 

 vikite with strong pleochroism in colours ranging from 

 light yellowish green to chestnut brown, is always in 

 subordinate amount, especially in coarse-textured varieties. 

 Pyroxene (diopside) rarely occurs except as a kernel in the 

 centre of the hornblende individuals. Biotite is usually 

 present in very small quantities. Sphene of characteristic 

 shape, apatite in comparatively large crystals, and mag- 

 netite, as accessory minerals, complete the list of constitu- 

 ents. 



Augite syenite. — The dark coloured augite syenite, 

 which occupies so large an area in the vicinity of Peninsula, 

 is one of the most interesting of the rock-types represented 

 in this district. It varies in colour from dark brownish- 

 grey to almost black. Transitional phases are dull 

 35069—2* 



