PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 729 



Greenwacke. Quartz schist.] 



No. 1444. GREENWACKE. 



Head of the portage from Fall lake to Garden lake. Replaces abruptly the jaspilyte at the head of the 

 portage. 



Ref. Annual Report, xvi, pages 111, 126. 



Greenstone. 



Mic. Hornblende in sharp, angular shreds and spicules, with secondary enlarge- 

 ments, and decayed feldspars. These seem to make up this rock, which has not a 

 distinct schistose structure. The appearance of the hornblende is in contrast with 

 that of No. 1439. Its spicules are sharp and fine, and twinning is not uncommon. 

 At the same time the crystals are ragged and defective, even the zonal enlargements, 

 and the sharp spicules. Chlorite and some of the old feldspathic element are within 

 them in irregular spaces. The feldspar grains are all small, roundish and much 

 decayed, having chlorite and apparently minute scales of Muscovite and of actinolite, 

 generated as secondary products. Still they are bound together in an interlocking 

 plexus of secondary fresh feldspar. That the hornblende was a product of alteration 

 from pyroxene is indicated by the remnants of that mineral still visible within the 

 larger hornblendes. A little leucoxene is disseminated in rather dark coarse groups. 

 One section. 



Age. Archean (Keewatin). N. H. w. 



No. 1446. QUARTZ SCHIST. (Magnetic. ) 



At the rapids between Garden and White Iron lakes (once known as Silver City). 



Ref. Annual Report, xvi, pages 112, 126 ; Bulletin vi, pages 8, 10, and plate V, figure 3. (Compare Nos. 950 

 and 951.) 



Meg. Thin-bedded magnetic quartz schist. 



Mir. Two sections have been made, and the description of Hensoldt was made 

 from them. They were very thick. On reducing one of them to the standard thick- 

 ness the parts all become more distinct. Magnetite is seen to be distributed not only 

 in somewhat regular bands, intermixed with quartz, but in finer particles is every- 

 where throughout the slide. The quartz is wholly of the secondary, interlocking 

 kind, and its grains are somewhat elongated prevailingly in the direction of the 

 structure. These two, with actinolite, constitute the rock. If there be any glassy, 

 fresh feldspar it is masked by its resemblance to the quartz, and none has been 

 detected. The 'actinolite is in fine detached needles or fibres parallel with the 

 structure. Two sections. 



Age. Keewatin (recrystallized). N. H. w. 



No. 144H. GREENWACKK. 



N. W. } sec. 4, T. 62-14. At a fresh drilling for iron, north of Mud lake. 

 Ref. Annual Report, xvi, pages 112, 126. 



Fine-grained, characterless greenstone. 



