GRANITE AND SYENITE OF LEICESTERSHIRE. 233 



Charnwood Forest. 



The igneous rocks of Charnwood Forest in Leicestershire l are 

 chiefly syenite, granite, and diorite. 



Syenite. The syenites occur in isolated masses in the neighbour- 

 hood of Groby, extending north-west from that place, where they are 

 surrounded by trias. At Cliff Hill the syenite forms a conspicuous 

 rugged ridge, and another mass is seen at Stanton Field; another 

 occurs at Hammer Cliff. All these exposures are termed by Professor 

 Bonney and Mr. Hill the southern syenites. At Groby the rock is 

 rather coarsely crystalline, and contains dark-green hornblende, with 

 pink and greenish felspar, with small masses of yellowish-green 

 epidote, and occasional grains of pyrites. When the rock is more 

 finely crystalline it is generally of a red colour. The rock is also 

 quarried at Markfield on Cliff Hill. It is generally traversed by bold 

 joints, which usually have a brown ferruginous coating. Under the 

 microscope the rock consists of orthoclase and plagioclase felspar, 

 often a good deal decomposed, and sometimes stained green, with 

 inter-crystallised quartz. The hornblende is often somewhat decom- 

 posed so as to appear fibrous, and it is frequently replaced by the 

 mineral epidote, and viridite. The quartz rarely occurs in grains 

 such as are seen in granite. Apatite is found in long clear six-sided 

 prisms. The more compact syenite consists chiefly of inter-crystal- 

 lised felspar and quartz, the felspar being sometimes replaced by a 

 zeolite. The quantity of hornblende is small. 



The rocks termed the northern syenites by Messrs. Hill and Bonney 

 are seen at Bawdon Castle, and to the north-west. A patch also 

 occurs at Great Buck Hill. At first sight the aspect of the rock is 

 different from that of the southern district, being less coarsely crystal- 

 line and more altered, passing occasionally into a dull green compact 

 rock. The circumstance that these rocks are rather more basic than 

 the others is associated with the view that they were probably less 

 deep-seated in their origin. Under the microscope the K>ck appears to 

 contain less quartz. The hornblende is almost entirely replaced by 

 products of its decomposition, such as viridite, chlorite, and epidote. 

 The iron is chiefly in the form of ilmenite. In so far as these rocks 

 differ from the typical syenites they make an approach towards the 

 diorites. 



Mount S orel Granite. On the left bank of the Valley of the Soar 

 is a mass of rock, forming the height called Buddon Hill and terminat- 

 ing at the village of Mount Sorel. Various outlying neighbouring 

 patches occur on the north-east and south-west, which are all probably 

 connected beneath the trias, so that the granite hills rise from the 

 surrounding strata as from a sea. The colour is usually pinkish, but in 

 the Mount Sorel pit it is sometimes grey. The rock is occasionally 

 slightly porphyritic, and consists of quartz, felspar, black mica, and 



1 Rev. E. Hill, M.A., and Professor Bonney, F.R.S., Quarterly Journal 

 Geological Society, vol. xxxiv. p. 211. 



