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GRANITE. 



223 



the Ordnance Survey. This mass of granite varies as 

 usual, in different places, affording fine building stones in 

 several localities, more particularly at St. Breward and 

 Blisland. — Rough Tor, near Camelford, Cornwall. 



14. — Granite, composed of two varieties of 

 (white and light brown), the former with a tend 



felspar 



form separate crystals ; common black mica and some* sil- 



very mica in foliated plates, and quartz. 

 Scilly Islands. 



15. — Granite, composed of two varieties 



Mary 



felspar. 



white and light brown, the former with a tendency to crys- 

 tallize separately — quartz and dark-coloured and silvery 

 mica. The specimen shews a weathered surface of quartz 

 and white felspar, from the decomposition of the mica and 

 brown felspar.— -Trescoe, Scilly Isles, near Oliver Crom- 

 well's monument. 



1 6. — Granite, composed 



varieties of mica, black and ivhite. 



felspar, and two 

 It belongs to the mass 



of granite noticed, No. 13. Used for building. Map 

 Camelford, Cornwall. 



17. 



flesh 



felspar, and black rnica^ Used for building. 



Guernsey. 



18. — Fine-grained granite. 



mica. 



Quartz, felspa 



The specimen shews a weathered surface, and is ap- 

 parently decomposing throughout.— Bryers, Scilly Isles. 



1 9. — Small-grained granite. 

 felspar, and mica, both black and m 

 End, Scilly Isles. 



Quartz, flesh 



St. Mary's, North 



20. 



Fine-grained granite, part of a vein traversing 

 serpentine. Map 32— Poltesco, Lizard, Cornwall. ("Re- 

 port on Devon and Cornwall," p. 173.) 



21— Fine-grained granite (very micaceous). This 

 specimen shews a weathering surface of a ferruginous- 

 brown colour, owing to the decomposition of the felspar. 



Map 31. — Near Tolvorn Passage, Falmouth Estuary, 

 Cornwall. J 



Upper 

 Gallery. 



Wall-cases 

 6 and 7. 





