PRECARBONIFEROTTS ROCKS OF CHARNWOOD FOREST. 



227 



the ground-mass rarely shows any brilliant colours, various shades of 

 pale yellow, milky white, and dull purple prevailing. The larger 

 felspar crystals, most of which are plagioclase, are also dull in 

 colour, though generally in fair preservation. Some, however, are 

 replaced by the minute bright-coloured microliths already noticed. 

 The quartz is generally rather free from cavities, and such as exist 

 are very small in size. The larger hornblende crystals, as has 

 been said, are often aggregated : they are rather irregular in form, 

 and appear to be affected by decomposition; possibly some are. 

 pseudomorphs after biotite. These last contain many irregular 

 microliths and aggregated specks, some of magnetite (?), others 

 of a semiopaque brownish granular mineral, which also occurs in 

 other parts of the field. The larger ferruginous grains are 

 also more abundant among the hornblende clusters. There is 

 not much viridite in this slide, and no distinct epidote. The rock 

 is generally nearer in structure to the felsites than to the normal 

 syenites, and would fall into the intermediate class, syenite-porphyry, 

 adopted by some petrologists. In the south-west corner of the 

 pit is a most interesting section. Here we find a highly altered 

 stratified rock. This is generally much stained and decomposed, 

 so that its nature is sometimes hard to recognize ; but careful 

 examination shows it to be a dull green, distinctly banded, slate, 

 very like some of those in the Forest. The syenite, as shown in 

 the diagram (fig. 2), is clearly intrusive in it, and partly overlies 



Fig. 2. — Diagram of Junction of Syenite and Slate in Pit South of 



Enclerby. 



Syenite 



A A. Indications of bedding visible here. 



the slate, so that very probably the latter was not exposed to view 

 until the pit was opened. There was last summer an excavation, 

 about six yards wide, below the general level of the pit, show- 



