TRIASSIC BRECCIAS AND CONGLOMERATES OF SOUTH DEVON. 75 



24. Porphyritic red and white quartz- and felspar-rock ; apparently 

 a vein-stone from " felspathic trap." Creditou. 



25. Grey-green felsite, finely granular texture, with porphyritic 



quartz, kaoliuized felspars, and some decayed mica. Crediton. 



26. Pine-grained crystalline-granular felsitic rock. Exminster. 



27. Reddish-grey quartzose felsite. Exminster. 



28. Dull-brown porphyritic rock, felsitic base with kaolinized por- 



phyritic felspars, Murchisonite, quartz, and mica. Some has a 

 brecciated look. Is closely allied to next. 



29. Deep-red porphyritic rock, varying to red-brown and purplish- 

 brown ; compact felsitic base with porphyritic quartz and 

 felspar, some of the latter kaolinized, some Murchisonite ; occa- 

 sionally but not invariably some mica. This is the so-called 

 red " porphyritic trap," more or less characteristic of the con- 

 glomerates within our area, from Torbay to the Crediton 

 valley, and the origin of which has been a special topic of 

 discussion. Save in colour, however, these fragments are 

 hardly distinguishable from some Dartmoor elvans. 



I have been fortunate enough to trace them home as veins to the 

 so-called " felspathic traps," in fragments of which I have found 

 them occur, both at Exminster and Teignmouth. They appear in 

 some instances to have produced contact-alteration. They are really 

 what they seem to be (porphyritic elvans), which have traversed 

 granites and " traps " alike, and are of purely local origin. They 

 have undergone as much alteration, probably, as any class of rock in 

 the breccias, ranging in texture from an earthy to a vitreous base, 

 but can be followed without difficulty from one phase to another. 

 One example really differs from the rock it intrudes on more in 

 structure than anything else, both showing felsitic characters, but 

 the vein being coarser and distinctively porphyritic. 



B. ScJiorlaceous. 



1. Granular schorlaceous pegmatite. Exminster, Teignmouth. 



2. Reddish compact felsite with blebs of quartz, a little mica, and 



schorl pseudomorphous after felspar, and in spots. Exminster. 



3. Variety of same rock, with somewhat granular texture, por- 



phyritic quartz, decayed felspars, and veined with schorl. 

 Exminster. 



4. Piner variety of same. Exminster. 



5. Pelsite like number one, with mica-aggregates. Exminster. 



6. Granular greyish-drab felsite, with acicular schorl. Exminster, 



7. Pine-grained reddish felsite, with porphyritic quartz and felspar, 



base sprinkled with black specks. Exminster. 



8. lied felspar- and schorl-rock. Exminster. 



9. Quartzo-felspathic rock with blobs of quartz, largo porphyritic 



felspars, and schorl. Teignmouth. 



10. Base black schorl and quartz, with porphyritic quartz and 

 felspars (kaolinized) ; a little mica. Teignmouth. 



