SCHORL ROCK. 



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The rock from which the specimen is taken contains large 

 crystals of felspar. In some parts of it, as is the case in the 

 specimen described (No. 56), the felspar crystals have been 

 removed by decomposition, and the cavities filled by crys- 

 tals of schorl crossing each other in various directions. In 

 such cases the schorl-rock base adjoining these refilled, or 

 nearly refilled, cavities, contains less schorl than around 

 the crystals of felspar which have not been decomposed, as 

 may be seen in the specimen. (See "Report on Cornwall," 

 pp. 160 and 161.) Map 33. — From the skirts of the granitic 

 mass close to Trevalgan, near St. Ives, Cornwall. 



57 and 58. — Schorl-rock, composed of a small-grained 



mixture of felspar and translucent quartz, with larger dis- 

 seminated portions and lines of schorl, traversing granite in 

 the manner of a dyke (elvan course), and holding a north- 

 western course towards the west of Chapel Cam Brea. (See 

 "Report on Cornwall," pp. 174 and 175.) Map 33. — Mayon 

 or Mean, near the Land's End, Cornwall. 



59. — Sciiorl-rock, formed, of nearly equal parts of schorl 

 and quartz, and containing larger detached portions of the 

 latter. This rock forms part of an elongated east and west 

 mass on the north of Belovely Beacon, and is separated 

 from the latter by an interval of altered slate, though pro- 

 bably it is connected with the granite and schorl-rock of 

 Belovely Beacon, at a comparatively insignificant depth. 



Map 



9 0. 



Small Money, Belovely Beacon, Cornwall. 



60.— Schorl-rock, an equal mixture of schorl smd quartz, 



with occasionally included larger portions of the latter. It 

 forms part of the schorlaceous granite of the line and mass 

 noticed below, No. 61. Map 30. — Penvivian Hill, near 



Bodmin, Cornwall. 



61. — Schorl -rock, schorl and quartz in nearly equal 

 proportions.— Roche Rock, Roche, Cornwall. 



This rock evidently forms a portion of the granitic mass 

 on the south of it, and of which Hensbarrow (1,034 feet 

 above the level of the sea) forms the highest part. The 

 skirts, generally, of this mass of granite from Penvivian Hill, 



Upper 



Gallery 



Wall-cases 

 6 and 7. 



