162 Macfarlane on the Primitive Formations 



1. Mica schist, " a slaty crystalline mixture of mica and 

 quartz,"* occurring most frequently and characteristic in the dis- 

 tricts of Tromsen and Senjen. It is, however, often found of a 

 more equivocal character, and is then called micaceous schist. It 

 presents numerous transitions into the other schistose rocks of the 

 group. Thus, gradually becoming fine-grained, it passes into clay 

 slate, micaceous clay slate, or argillaceous mica schist, and by the 

 disappearance of the mica, through quartzose mica schist, into 

 quartz slate. Similarly, when chlorite and talc occur in it, it often 

 becomes a chloritic or talcose mica schist; the former of these being 

 the most frequent. 



2. Clay slate, " an impalpable (indistinctly mixed,) distinctly fo- 

 liated, soft rock ; generally of a greyish, greenish, or bluish col- 

 or,"! appears to be, next to mica schist, the most frequently occur- 

 ring rock. It is however, more developed in the districts around 

 Trondhjem, and is of a more variable character than even the 

 mica schist. Besides the many varieties that may be included 

 under the general term of argillaceous slate, which is frequently 

 applied to these rocks, there occurs a clay slate, described as be- 

 ing both micaceous and chloritic, (Chloritischer Thonglimmer- 

 schiefer) ; from which it appears that, even mechanically, the same 

 substances are distinguishable in some clay slates, which Sauvage 

 found by chemical analysis to be present in the slates of the Ar- 

 dennes ; viz., a chloritic mineral which was decomposed by hy- 

 drochloric acid, with a micaceous mineral decomposable by 

 sulphuric acid, and quartz.]; 



8. Chlorite schist, " a soft schistose, mostly greenish colored 

 rock, consisting principally of chlorite. Quartz or feldspar, or 

 both together, are however frequently mixed with the chlorite."|| 

 It is often found in its characteristic form, but is also frequently 

 described merely as chloritic schist, and occurs principally in the 

 districts around Trondhjem. 



4. Limestone comes next in frequency. It is developed especially 

 in the districts of Tromsen and Senjen, where its texture varies 

 from granular to impalpable, and its colour from white to dark 

 grey. The limestone of the districts around Trondhjem, is mostly 

 yellowish-white, and of an impalpable, sometimes slaty structure. 



♦ Lehrbuch der Geogaosie II, 281. 



t Gotta : Gesteinslehre, p. 140. j Idem, p. 147. 



i Ann : des Mines VII, 441. 



II Gotta : Gesteinlehre, p. 145. 



