part 2] GEOLOGY OF THE MELDOX VALLEYS. 81 



the contact-shale is highly tourmalin ized, the mineral being brown- 

 grey with rare blue shades, in small prisms and grains. The 

 ground-mass is cryptocrystalline quartz, with a very little apatite 

 and sphene. 



LXXVI, S.E. 31 a, another aplite-vein, yields contact-shale with 

 much very pale mica and rather numerous small prisms of pale 

 brown tourmaline. 



LXXYI, S.E. 32 a. Redaven. The shale at the contact with 

 a granite-dyke is highly micaceous, both white and brown micas 

 being present. Small brown tourmalines, with occasional shades 

 of grey, are frequent. There are many patches of andalusite, 

 mostly granular, but in part prismatic with clearly-defined pink 

 pleochroism. No. 32 c, from the contact with a narrow vein im- 

 mediately north of 32 a, contains no andalusite, and much of the 

 brown mica is altered to chlorite. 



LXXVI, S.E. 46, in contact with a vein of granite a few inches 

 wide, in the bed of the western tributary of the Redaven. The 

 altered shale is highly micaceous, the mineral varying from colour- 

 less to pale brown, and some being altered to chlorite ; there are 

 a very few small tourmalines, pleochroic from colourless to deep 

 red-brown, and a little green tourmaline is present. Granular 

 prismatic patches of andalusite. A little rutile. 



At LXXVI, S.E. 62, on the Flushcombe, the immediate junc- 

 tion is marked by much pale-brown tourmaline mingled with red- 

 brown mica ; be} r ond this the rock consists of red-brown mica, 

 granular andalusite, and quartz-mosaic, with small stout rutile- 

 prisms regularly distributed. 



LXXVI, S.E. 4, bed of the West Okement above Vellake Corner. 

 The shale in contact with a narrow granite-vein is crowded with a 

 pale mica, contains a little tourmaline colourless to rich cinnamon- 

 brown, and a few 7 grains of rutile. There is no andalusite in the 

 shale, but a fair amount in the granite. 



LXXVI, S.E. 9, quarry by Vellake, another aplite-vein occurs 

 here, and the contact-slate develops andalusite and pale-grey mica. 

 Rutile is prominent in all the shale from this quarry. 



Andalusite is thus the one additional mineral brought in by the 

 intensive action of the dykes and veins ; but the mica is increased 

 in quantity and altered in colour, and the tourmaline is usually 

 increased also. 



Within the area considered there is no real tourmalinization of 

 the shales on a large scale ; an occasional band may be met with, 

 as at LXXVI, S.E. 45 a, on the western tributary of the Redaven : 

 these bands are, however, but a few inches wide at the most. 

 Farther east, south-east of Anthony Stile, the shales are extensively 

 tourmalinized. 



The constant references to rutile will have been noted : in my 

 experience one feature of metamorphism by intrusive igneous rocks 

 is that the clay-slate needles, if originally present, either disappear 

 or are replaced by much stouter forms. 



