Ii!fTEEESTING LOCALITIES OF ^EGAUiTEE EOEMATION. 387 



micaceous lieinatite. As is usual, the crevices fonneil bv the folding, both 

 jjarallel and transverse to the lamination, are healed by crystalline mao-- 

 uetite. No transition varieties between the jasper and the g-riineritic rocks 

 were here seen. The annular area where such rocks would occur, if they 

 exist, shows no exjjosures. 



At the south end of the Barron mine, at the southwest end of the bluff, 

 it is said that a diamond-drill passed at once from the jasper to the granite. 

 If this be true, the Ajibik quartzite is here very thin, and it is not impossible 

 that the whole of the Lower ^Marquette series for some distance west of 

 Mount Humboldt was cut out by the inter-Marquette erosion. 



Under the microscope the griineritic rocks on Mount Humboldt for the 

 most part prove to be but slightly (juartzitic, being composed almost wholly 

 of griinerite and iron oxides. Many of the slides consist of a nearly solid 

 mass of griinerite, in which is contained comparatively little iron oxide. 

 While the blades to some extent are in various dii'ectious, there is a distinct 

 tendency for the longer axes to have a parallel arrangement. These grii- 

 nerite rocks grade into those in which the magnetite and hematite are-- 

 plentiful. Of the iron oxides, magnetite is predominant, and the hematite- 

 seems to be, in pai-t at least, an oxidation product of the magnetite. Much 

 of the magnetite is in crystals or clusters of crystals. Where the iron 

 oxides are abundant they are usually more or less concentrated into bauds. 

 Sometimes the parallel blades of griinerite, following the schistosity, are 

 diagonal or perpendicular to the bands of iron oxide. Not infrequently the 

 magnetite-griinerite-rocks are garnetiferous. The garnets include a large^. 

 amount of griinerite in the griinerite-rocks, and of magnetite and griinerite^ 

 in the magnetite-griinerite-rocks. The griinerite needles may be seen pen- 

 etrating the garnets in all directions. The garnets appear to have been the- 

 latest development and to have included or absorbed the jireviously existing 

 minerals. These garnetiferous varieties are particularly abundant adjacent 

 to the greenstone masses and at low horizons. In some cases between an 

 intrusive greenstone and a griinerite-magnetite-rock there is an almost solid' 

 layer of garnet. In a number of cases associated with the griinerite is a 

 pleochroic green hornblende. This green hornblende occurs as inde^jend- 

 ent blades and as parts of blades. In the latter case a blade of amphibole 



