164 CHLORITE SCHIST. 



of Tymlrum holds an ambiguous place between this 

 and quartz rock, producing zinc and lead ; and, in 

 other places in Scotland, it contains lead and copper. 



Chlorite Schist. 



Although this does not, like micaceous schist, ap- 

 pear to form large tracts of country, or alone to con- 

 stitute mountain masses, it is far too important to he 

 classed as a variety of that rock. That it has not 

 found a place in former geological arrangements, is 

 no reason for excluding it from the present. 



Its frequent connexion with micaceous schist, to- 

 gether with its analogy in structure and composition, 

 render this its natural place ; yet it will be found to 

 possess a much greater variety, under that principle of 

 arrangement by which I have classed,, under one title, 

 all those hitherto unnamed rocks, which are associated 

 by geological position, by the existence of a predo- 

 minant or characteristic mineral, and by a frequent 

 transition into each other. The details of these will 

 be found in the Classification of Rocks ; while, re- 

 specting its general definition, it is that of micaceous 

 schist, substituting foliated chlorite for mica. The 

 description of the great features of micaceous schist, 

 apply equally to this rock, as far as it is known to 

 me ; since they most commonly occur together, either 

 in a simple association, or in alternation with others. 

 Where intermingled, in minute and frequent alterna- 

 tions, with other strata, it can confer no peculiar fea- 

 tures on the aspect of a country. 



Chlorite schist is best known as accompanying 

 micaceous schist ; forming, in this case, irregular beds, 

 of greater or less extent, sometimes alternating with 

 that rock, bnt more frequently graduating into it, so 

 that the limits are undefinable. Thus it is often im- 



