AMPHIBOLHK> AND RELATED R<"H- Mil I \\KLL. 279 



orthoclase, and a subordinate amount of plagioclase. The abundance of microcline 

 and the dec Teased amount of epidote bring the rock into the group of the alkali felspar 

 gneisses, and it may be called a chlorite-microcline-gneisB. 



Another porphyroblastic epidote-felspar-gneiss is No. 590; but it differs from 

 the two preceding specimens in possessing a marked schistose structure. It consists 

 of porphyroblasts of pink felspar, set in a base coloured green by epidote. The 

 porphyroblasts consist of granoblastic aggregates of untwinned and microcline felspar. 

 The <-loar base consists of felspar with a few grains of quartz and a subordinate 

 amount of plagioclase. Coarse crystals of epidote are abundant and grouped in 

 (luster.-, witli chlorite and a little zoisite. llmenite has been altered to leucoxene. 



Specimen No. 910 is a different type, and may be described as an epidote-felspar- 

 breccia. It is a very dense, fine-grained, pale-greenish rock studded with minute 

 porphyroblasts of felspar. The thin section possesses a uniform pale-green colour, 

 and consists of angular crystals of felspar set in a dark semi-opaque mass of epidote. 

 The general appearance is that of a breccia and the felspar is water clear, partly twinned 

 and partly untwinned. Some of the lamellar-twinned individuals have an extinction 

 angle of 16. Here and there are larger crystals of epidote, which are more transparent 

 than the base, and consequently show brilliant polarisation colours. Under high 

 powers the base of the rock is seen to consist of closely packed minute grains of epidote 

 set in a base of clear felspar. 



Specimen No. 592 is a massive, pale-greenish rock, somewhat similar in appearance 

 in section to the coarse-grained variety, No. 726. It contains coarse crystals of partially 

 altered honibjende, epidote (sometimes intergrown with allanite), chlorite and felspar. 

 The rock is brecciated, and the fragments are separated by veins of quartz and felspar, 

 darkened by finely granular epidote. 



Specimen No. 591 is an epidote-felspar-gneiss, which has a pale-green colour 

 and a schistose structure. In section, it shows the helical structure commonly seen 

 in phyllites and mica schists. There are a few small felspar porphyroblasts, some of 

 which are cracked and broken, and show various stages in breaking down into a finely 

 granulitic mass. Some felspars are untwinned, and some are acid plagioclase. There 

 are also a few porphyroblasts of allanite. The bulk of the rock consists of the finely 

 granulitic base enveloping the wavy bands of dark granular epidote, similar to that in 

 No. 910. Chlorite is present, and interwoven with the granular epidote, and there 

 are occasional crystals of sphene. The specimen assumes a dark colour on the one side, 

 where the amount of felspar decreases and the rock passes into an epidosite. 



A further stage of epidotisation exists in specimen No. 589. This specimen 

 rot.iins the schistose structure and possesses traces of green hornblende. The felspar 

 is subordinate, and there are bands of well crystallised epidote, as well as bands of 

 finely granular epidote. Lawsonite is also present, and has been derived from the 

 feNpar. In addition there is a little zoisite and abundant sphene. 





