part 2] THE METAMORPHOSED ROCKS OE THE START AREA. 187 



while the calculated mode gives :- 



Per cent. 



Hornblende 47'5 



Epidote 22-5 



Albite 23-7 



Per cent. 



Chlorite 2-0 



Titanite 3'7 



Analysis VII shows that the hornblende must be of an alu- 

 minous type. The approximate composition, as calculated from 

 the analysis, is CaO 11 per cent., MgO 16, FeO 15, A1 2 3 9, and 

 SiO„ 48. A comparable hornblende is that of the hornblende- 

 dacite from San Pedro, Sierra del Cabo, Cabo de Gata (Spain) : 

 see Whitman Cross & others, ' Quantitative Classification of 

 Igneous Rocks ' 1903, Table XIII c. 



When this analysis (VII) is compared with that of the 

 chlorite-epidote-albite-schist, it will be seen that the main dis- 

 tinction is the higher lime content and lower soda content of the 

 former. By advance in metamorphism, chlorite has given place to 

 hornblende, partly at the expense of epidote and probably also 

 by reaction with calcite. With this increasing metamorphism the 

 character of the plagioclase slowly changes. A more calcic type 

 of felspar is stable under higher-grade metamorphic conditions. 



As has been noted above, rocks of this type are widely distributed 

 in the Start Green Schists, but no zonal areas can be differentiated. 

 Other notable localities for hornblende-schists are Bolt Tail, and 

 Inner Hope, Southpool Creek, and Spirit of the Ocean Cove, near 

 Start Point, where an isolated mass of Green Schist is found 

 among the mica-schists. This latter rock has been described by 

 Dr. A. Harker, and his description is quoted by W. A. E. Ussher 

 in the Geological Survey Memoir, p. 51. The mineralogy of this 

 rock is essentially similar to that of the Prawle Point rock. 

 Epidote is more abundant, and the distribution of the albite is 

 somewhat different. In this rock it forms granular aggregates of 

 lenticular shape, and between the lenticles are developed amphibole, 

 epidote, and titanite, with chlorite. Calcite is also present. It 

 is possible that this rock represents a sill-intrusion in the Start 

 mica-schists. 



In other members of the hornblende-epidote-schists, such as, for 

 example, a band at Seacombe Sands, the hornblende does not form 

 stout porphyroblasts, but is wholly developed in long colourless to 

 pale-green fibres with marked cross-parting, associated with epidote 

 and less abundant chlorite, and separating lenticular areas of albite. 

 With this development the schistose texture is strongly marked. 



(iii) Nodular Masses in the Green Schists. 



At various points in the Green - Schist outcrops east of the 

 Salcombe estuary, notably in the vicinity of Limebury Point and 

 Hamstone Cove, yellow to yellow-green nodules are found in the 

 Green Schists. Owing to their more resistant weathering, these 

 masses stand out from the face of the rock. The nodules range in 

 greatest diameter from 6 inches to less than 1 inch, but measure 



