AMPHIBOL1TES AND KKI.ATKI) l >. K> - I I l.l.\\ KLL. 271 



III. GROUP V.-MACNKSHM S1IJCATK (JNEISSKS. 



As the percentage of felspar decreases the members of the Amphibolite Group 

 grade into the rocks of Group V, the magnesium silicate gneisses. 



KATA DIVISION. 



Assigned to the Kata division of Group V is Specimen No. 527, an apple-green 

 rock, consisting essentially of granular green pyroxene. It consists, in section, of a 

 granulitic mass of clear pyroxene, resembling oniphacite, with a subordinate amount 

 of very pale green to colourless hornblende, together with a little interstitial quartz. 

 Garnet is absent; and, otherwise, the rock would be classed as an eclogite in Group IV. 

 The development of hornblende is irregular, and sometimes is accompanied by a little 

 biotite. Portions of the specimen possess a distinctly dark-green shade, due to an 

 increased amount of hornblende. One portion of the specimen possesses a noticeable 

 percentage of red felspar, indicating the relationship with the amphibolite group. 

 This particular specimen is traversed by a vein of quartz and plagioclase, 2 cm. wide, 

 in which the quartz is mostly confined to the cent re of the vein, and the plagioclase 

 to the walls of the vein. 



In Specimen No. 963 the hornblende is much more important, and the hand 

 specimen possesses a corresponding dark colour. This specimen was obtained from an 

 erratic on Cape Hunter. The main constituent of the rock is pyroxene, including 

 both augite and hypersthene. Some of the crystals are clear and granular, and others 

 are fibrous. All show more or less alteration to hornblende. There is a small 

 development of brown biotite accompanying the hornblende, subordinate plagioclase, 

 and scattered grains of ilmenite and pyrite. 



These rocks are unfoliated, and therefore possess resemblances to the ultra 

 basic igneous rock " pyroxenite " ; but the pyroxene possesses the distinctive 

 character of the granular pyroxene of metamorphic origin commonly observed in the 

 Cape Gray series of altered basic dyke rucks. 



MESO DIVISION. 



As hornblende becomes the essential constituent the types are grouped in the 

 Meso division of Group V. Among these is Specimen No. 594, a garnet-hornblende- 

 schist. It is a coarse-grained, dark-green rock, which consists of green hornblende 

 and scattered pink garnets. In addition, there is a little interstitial felspar, as well 

 as scattered grains of ilmenite and apatite. 



Specimen No. 513 is a heavy, dark-green, slightly schistose rock, consisting 

 essentially of amphibole, with scattered specks of pyrite visible in the hand specimen. 

 In thin section there are large talcose areas produced by the decomposition of some 





