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Specimen No. 915 is an example of a garnet-biotite-amphibolite with glomero- 

 phisnutic structure, and is similar to No. 50 (PI. XLI, fig. 1). In section, it is found 

 that the dark areas of hornblende crystals consist of small lenticular clusters, together 

 with biotite and ilmenite. The white areas are granoblastic aggregates of basic 

 plagioclaae. A similar specimen is No. 990, in which the brown liiotite is replaced by 

 ii <-hlorite. and more of the felspar is saussuritised. 



No. 339 is a garnet -bearing gabbro-gneiss (PI. XLI, fig. 2). It possesses a coarse 

 gneissic structure, and has a mottled appearance. The black areas consist of 

 aggregates of hornblende and augite, or garnet and biotite, but the four minerals are 

 contained in some aggregates. The white areas, which are slightly discoloured by 

 weathering, consist of aggregates of labradorite, partly saussuritised, and a little 

 quartz. The biotite aggregates contain a little lawsonite, and their rounded form 

 suggests their derivation from garnet 1 . The suggestion is supported by the 

 presence of quartz, which can be formed with the change from garnet to biotite. The 

 hornblende has been derived from augite, while the granular form of the metamorphic 

 pyroxene suggests its derivation from large platy pyroxene crystals. Ilmenite and 

 apatite are accessory minerals. The microscopical features are similar to those of the 

 hornblende-pyroxene-gneisses, with the addition of the glomeroplasmatic structure. 



A specimen in which the gabbro structure is very prominent is No. 593, whose 

 character would be well described as a hornblende-gabbro. It is a coarse, handsome 

 rock, containing some large crystals of labradorite, though consisting for the most part 

 of coarse hornblende and felspar. Occasional crystals of green augite are associated 

 with the hornblende, and a few fragments of garnet are found near plates of biotite. 

 In thin section the labradorite has a tendency to idiomorphic outlines a contrast 

 to the granoblastic aggregates of many metamorphic rocks. The twin lamella; of the 

 labradorite are very broad and much more abundant than in previous types, but there 

 is a small amount of untwinned sodic felspar. The hornblende forms large crystals, 

 but in other respects is similar to the smaller crystals in the amphibolites. Augite is 

 present, and in one case forms the nucleus of a large hornblende crystal. Large 

 crystals of ilmenite, with sphene rims, accessory apatite, and zircon are present. 

 While the nature of the rock is understood by the name " hornblende-gabbro," the 

 rock possesses metamorphic traits in the presence of relic garnet, of secondary felspar, 

 saussuritised felspar, and the characteristic relation of sphene and ilmenite. 



In specimen No. 367 some of the felspar areas are 2 cm. wide, and the rock has 

 the appearance of an augen gneiss. The section shows that the felspars have 

 recrystallised as granoblastic aggregates of calcic andesine, fairly free from saussurite. 

 ii-se crystals of epidote are present. Some of the biotite is replaced by chlorite 

 and is intergrown with lawsonite. The Epi zone features are, however, subordinate 

 in this example, and the rock may be called a plagioclase-gabbro-gneiss. The 

 plagioclase is thoroughly saussuritised in a somewhat similar specimen, No. 969 

 (PI. XLI, fig. 3). 



Op. oit., p. 167. 



