FROM THE ISLANDS OFF THE LIZAKD. 



315 



pr tonalite, and may be described as a tonalite-gneiss. The granu- 

 lation of the quartz and the felspar in certain portions of the rock 

 is probably a consequence of the dynamic metamorphism which has 

 affected the district. 



Vasiler. — The specimens are similar to those from Men Hyr. 



Clidf/as EocJrs. — (1) Coarse tonalite-gneiss of the Men Hyr type. 



(2) A greenish-black rock (greenstone) with occasional crystals 

 of porphyritic felspar. Under the microscope the porphyritic felspars 

 are turbid and without individual action on polarized light ; they 

 lie in a ground-mass of hornblende and granulitic w^ater-clear 

 felspar. Grains of iron-ore and a few yellow prisms and twins of 

 rutile are also present. The hornblende forms the greater portion 

 of the mass ; it occurs in extremely ragged patches and only here 

 and there shows traces of crystalline form. The terminations of 

 the longer patches sometimes run out into actinolitic needles. The 

 granulitic felspar plays the role of matrix to the hornblende. The 

 individual grains are as a rule untwinned, but the larger of 

 them occasionally show striation. The hornblende is probably 

 secondary after augite, and the rock may be termed a porphyritic 

 epidiorite. 



Man of War. — (1) Coarse tonalite-gneiss. A specimen from the 

 east end of the Post differs from the one described from Men Hyr 

 only in containing more hornblende and garnet. The latter mineral 

 occurs in well-formed crystals. 



(2) Porphyritic greenstone (epidiorite) and actinolite-schist. Mr. 

 Fox's sketches show that the rock-masses have been deformed 

 since the dykes were intruded. We find evidence of this in the 

 dykes themselves. In one specimen the greenstone, near its junction 

 with the gneiss, has become a felspathic actinolite-schist. The 

 actinolite-schist differs from the epidiorite of the Clidgas in possessing 

 very perfect schistosity and foliation, and in having the whole of its 

 hornblende in the condition of actinolite. The porphyritic felspars 

 form "eyes" in the actinolitic schist. 



Taylor''s Bode. — (1) Gneiss. A section of one of the coarser 

 gneisses from this island shows an irregular granulitic aggregate of 

 quartz and felspar, the latter often striated, and actinolitic horn- 

 blende, which may be either brown, green, or nearly colourless. 

 Iron-ores, garnets, and zircons occur as accessories. This rock 

 differs from the tonalite-gneiss of the Men -Hyr type in the extent 

 to which the granulation of the quartz and felspar has been carried 

 on. It might on this account be designated a granulitic gneiss, 

 reserving the term granulite for a rock in which the quartz and 

 felspar are present wholly in the form of a micro-crystalline mosaic 

 of fairly uniform grain. 



(2) Porphyritic greenstone (epidiorite). 



The Stags. — (1) Moderately coarse-grained tonalite-gneiss con- 

 taining garnet and sphene as accessories, and having the foliation 

 imperfectly developed. 



(2) Lighi>-col cured, fine-grained granulite or granulitic gneiss, 

 with well-marked foliation. 



