MIC.VCEOUS SCHIST. 275 



Carbonat of lime occurs in a similar manner, 

 but rarely. 



Many minerals, hereafter noticed in the Sy- 

 nopses, are occasionally found imbedded in this 

 rock. Among these, garnet is eminently con- 

 spicuous ; as it sometimes abounds to such a 

 degree as almost to equal in quantity the includ- 

 ing rock, and thus materially to affect its charac- 

 ter. Whatever singularity or beauty such varie- 

 ties may present, from containing one or more of 

 these extraneous minerals, they require no further 

 notice than that which is given of them in the 

 list appended to the catalogue of varieties. 



The colours of micaceous schist offer very 

 little variety. With the exception of those which 

 contain a conspicuous quantity of imbedded ex- 

 traneous minerals, or pass into chlorite schist, 

 they present tints of grey alone ; the mica vary- 

 ing from white to black, and the quartz being 

 almost invariably colourless. The degree of 

 colour, in these cases, depends chiefly on. the 

 proportion of mica in the compound. 



T 2 



