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FELSPAR PORPHYRY OR ELVAN. 



233 



77.— Felspar porphyry (elvan dyke, near a lode), com- 

 posed of crystals of quartz and felspar and «es& of schorl 

 Map 31. — Consols Mines (west end), Cornwall. 



78. — Felspar porphyry, composed of a grey felspathic 

 base, containing disseminated hornblende, and vessels filled 

 with calcareous matter. Forms part of one of several elon- 

 gated trappean masses which occur near Endellyon. (See 

 Geological Map No. 30.) They vary in mineral struc- 

 ture, even at short distances, in the same mass. Judging 

 from the phenomena observable on the adjacent coast, these 

 masses of trap have been intruded among the slates of the 

 district, which slates are fossiliferous. Map 30 Endellyon, 



Cornwall. 

 79. 



coloured f el sp 



a felspatho-quartzose base. 



composed of crystals of flesh- 

 schorl, with veins of quartz in 

 It forms an elvan dyke in 

 which tin branches are found. (See "Report on Cornwall " 

 p. 175.) Map 33. m " — ' 



wall. " ' "" *" 



80.— Granitic rock, composed of a grey quartzo-felspa- 



thic base, with included imperfect crystals of lighter coloured 



Mine 



felspa 



It forms the north-east 



30) 



( 



Treburget, near St. Teath, Cornwall. 



81.— Felspathic porphyry, (part of an elvan dyke,) 



ft 



iff* 



and apparently others of schorl It forms a variety of 

 No. 102 ; it would be a beautiful ornamental stone. Map 

 30.— Tremore, near Bodmin, Cornwall. 



82.— Felspathic porphyry, forming part of the same 

 dyke (No. 89) where it abuts against the slates anion" 

 which it has been intruded. The different structures of 

 the different parts of the dyke may be explained 



No. 97. 

 Cornwall. 



Map 31. 



as at 



Cliff, South of Penhale, Crantock, 



Upper 

 Gaxleky. 



"Wall-cases 

 6 and 7. 



