various parts of Scotland, 437 



is, however, intermixed with rocks, consisting of hornblende, and 

 felspar, and of micaceous schist mixed with hornblende. It exhibits 

 therefore, specimens of the syenite of Werner, but such as are evi- 

 dently associated with the mica slate family, and perfectly distinguished 

 in their connexions, from the greater bodies of syenite occurring in 

 Scotland, which appear in an independent position, resembling that 

 of the trap family. The mica slate is often remarkable for contain- 

 ing numerous and very large cubical crystals of pyrites, an occur- 

 rence much less frequent in this rock than in clay slate. 



Veins of quartz traverse it in innumerable places, and it is also 

 Interspersed with compressed nodules of quartz, which bear no 

 marks of attrition, but are intimately united to the mica slate, or 

 chlorite slate, in which they occur. They are frequently character- 

 ized by a beautiful transparent brown colour, which renders them 

 objects of much research and high price among lapidaries. 



Massive chlorite also appears in abundance, and it is generally 

 interposed between the chlorite slate and quartz nodule. But the 

 object for which I have chiefly noticed this mountain, is the occur- 

 rence in it of Rutlle, a mineral as yet of sufficient rarity to deserve 

 a record of all its habitats. It is found in the larger, as well as in 

 the smaller quartz nodules, and exhibits many of its well knov\^n 

 varieties. 



The crystals generally penetrate the quartz, and often appear to 

 have their bases fixed in the investing chlorite. It is worthy of re- 

 mark, that although they most commonly penetrate the quartz, as if 

 crystallized at perfect liberty, yet they are frequently bent, so as to 

 accommodate themselves to its occasional elevations and depressions. 



Our knowledge of the chemical laws by which mixed minerals are 

 crystallized together is as yet so imperfect, that we can offer no 

 conjecture on an appearance so complicated as this, which however, 

 is not the less deserving of our attention. 



