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reddish-grey or soapy brown. Freshly broken surfaces 

 exhibit the brightly gleaming surfaces of plate-like or 

 lath-shaped feldspar. These idiomorphic feldspars are 

 frequently Carlsbad twins, often with a handsome bluish 

 shimmer. The feldspars are greatly predominant, but, 

 owing to their prevailing dark colour, which is due to 

 inclusions, the relative paucity of bisilicate material is 

 not noticeable except upon close inspection. The rock 

 is coarse in texture, the feldspars averaging a quarter of 

 an inch ((-6 cm.) in length and breadth, but only a tenth of 

 an inch (-25 cm.) in thickness. 



The mineral constituents are principally feldspar and 

 pyroxene with subordinate amounts of hornblende, biotite 

 and olivine; magnetite, apatite and pyrite are accessory 

 constituents. The feldspar is for the most part a micro- 

 perthitic intergrowth of albite and orthoclase, although na- 

 tron-orthoclase, orthoclase and plagioclase are also present, 

 but are relatively unimportant. Pyroxene is the character- 

 istic dark mineral. In the Peninsula area this mineral 

 shows a pale brown interior with a deep green border, and 

 is undoubtedly one of the aegirine-augite series. In out- 

 crops, near Coldwell as well as between the crossing of 

 Little Pic river and Middleton station, the augite is pale 

 violet, sometimes bordered by brown barkevikite. In 

 the western part of the Peninsula area the pyroxene is 

 commonly diopside, frequently surrounded by a border 

 of brown barkevikite and bright blue arfvedsonite. Olivine 

 is usually present but is not an abundant constituent 

 except in the vicinity of Middleton. The rock in the 

 cutting east of Penisnula near Craig's gravel pit contains 

 an olivine which, between crossed nicols, resembles sphene. 

 It was identified by Brogger, who states that it corresponds 

 very closely with the olivine present in the laurivikite of 

 southern Norway. Hornblende, usually barkevikite, occurs 

 sparingly. Arfvedsonite is also noticeable, and very 

 occasionally riebeckite, distinguished by its pleochroism 

 in deep bluish colours. Biotite is an unimportant consti- 

 tuent. Magnetite, pyrite, apatite, and bluish fluorite 

 are the accessory constituents present. 



White feldspathic variety. — The white feldspathic 

 variety, which is closely related to the nepheline syenite 

 occurs about the centre of Big Pic island. The white 

 feldspar, which is by far the most abundant mineral, is 

 chiefly orthoclase or albite or graphic intergrowths of these. 



