part 2] OF SOIJTHEEIN^ EYEE PENINSULA. 119' 



occasionally the Bavenolaws — in addition to the albite lamella tion. 

 The newly-formed minerals include secondary augite, hypersthene, 

 and garnet. As before, the secondary granulitic aiigite forms a 

 border to the ' relict ' augite. All fine dusty magnetite has been 

 eliminated, or at least has coalesced into larger granules, which 

 become associated with the secondar}^ augite-granules. 



The garnet is likewise developed in granular fashion, but, when 

 wholly enclosed in felspar, quite well-developed idioblastic dode- 

 cahedra are the rule. It may occur as a corona or border to the 

 pyroxene, intervening between this mineral and the plagioclase- 

 felspar (see fig. 9, p. 120). Very characteristic, however, is its. 

 presence in granulitic aggregates or complexes consisting of garnet, 

 augite, and hyj)ersthene, with magnetite and usually biotite. 

 These complexes may be developed around central grains of diallagic 

 primary augite, the garnet often then forming an outer border to 

 the felspar (see fig. 10, p. 120). The secondary augite of these 

 complexes is typically granulitic, with high double refraction, 

 oblique extinction, and not sensibly pleochroic. The hj^persthene 

 is developed with the same habit, but shows a strong pink to green 

 pleochroism, is oj^tically negative, and has straight extinction. 

 The garnet is likewise granulitic, and sometimes presents a core of 

 opaque grains of magnetite. In some of the grains occur inclusions 

 of microvermicular pyroxene. Magnetite may also appear as a 

 corona of grains around the pyroxene-granules. 



The absence of quartz from these complexes, and indeed from 

 the whole rock, is of noteworthy significance. There appears to be 

 only one interpretation of these aggregates : namel}^, that they are- 

 the products of recr3^stallization of an original primary augite. 



The small amount of hornblende present replaces the pyroxenes,^ 

 for the habit is distinctly preserved. Biotite, too, is a secondary 

 product ; but its development is more clearly associated with the 

 iron-ore, from which it has presumably derived some of its iron 

 supply. It is of the characteristic red-brown type. 



The specific gravity of this rock is 3"13. 



No. 221. — This represents another band from the same locality. 

 It resembles those previously described in many particulars, but is 

 characterized by an additional mineral, olivine. This is developed 

 in colourless grains with a high refractive index. Characteristically 

 along cracks are seen aggregates of magnetite-grains. Serpentine- 

 pseudomorphs after this mineral are present, and their strong green 

 colours are indicative of a high iron-content. A yellowish-brown 

 type of serpentine is also occasionally met with, and has no 

 perceptible pleochroism. Suitable sections of the olivine show that 

 it possesses negative birefringence, and its ferrous content must 

 therefore exceed 12 per cent. Man}^ of these olivine-grains show 

 a border of pleochroic hypersthene, which in some cases is granu- 

 litic. It appears probable that this border must represent a 

 primary crystallization, indicative of the conditions of mobile 



