INDEX. 



IX 



Quartz RoL-k, intrusive character of, 49 ; 

 microsL'opic study of, from Lake Superior 

 Mine, 4y. 



Quartz, Veinstone, microscopic examination 

 of, 51 ; Uuid cavities with moving bubbles, 

 51. 



Quartzitc, of Brooks, at Republic Mountain, 

 34, 35 ; of Garp River, 9 ; defined by 

 Zirkel, Lasaulx, and llawes, 58 ; eruptive 

 form of, 'Hi, 35 ; eiuptive origin of, 11 ; 

 formed of detritus of jasper and iron ore, 

 59 ; granite intrusive in, 55 ; Iluronian 

 age of, 23 ; an indurated sandstone, 58, 

 59 ; microscopic study of iron ore intru- 

 sive in, 33 ; microscopic study of, from 

 Ishpcining, 59 ; microscopic study of, 

 from Jackson Mine, 59, 60 ; microscopic 

 study of, from New York Mine, 59 ; mi- 

 croscopic study of Brooks's, from Repub- 

 lic Mountain, 54 ; of the New York Mine, 

 30 ; origin of, 9 ; overlying ore, and con- 

 taining fragments of it, 32 ; ripple-marks 

 in, 9,^25. 



Quebec Group, Lake Superior sandstone be- 

 longing to, 93. 



Quincy Mine, working on an old lava flow, 

 125 ; character of ore deposit, 129. 



Raindrop impressions in shale, 121. 



Republic Mountain, diorite of, 45, 47, 49 ; 

 granite of, 52-55 ; greisen of, 44, 55 ; 

 magnetic silicious schist of, 47 ; ore and 

 rocks of, 34 ; " quartzite " of, 34, 35. 



Rhvolites, fclsites originally identical with, 

 38, 39, 118, 119. 



Rhodochrosite, at jMcConiber Mine, 51. 



Ripple-marks, 9, 25, 79, 121. 



Rivot, L. E., his ideas in regard to Lake 

 Superior geology, 11, 12, 91. 



Rominger, C, on the conformability of 

 Laurentian and Huronian, 25 ; dikes near 

 Marquette, 36 ; on the geological age of 

 the Eastern sandstone, 122 ; on occurrence 

 of " soft hematite," 50 ; on the Ontonagon 

 district, 104, 105; on Presque Isleserpen- 

 tine,62 ; on the relation of the copper-bear- 

 ing rocks to the sandstone, 103, 104 ; on 

 the relation of the sandstone and qnartzite, 

 22, 23. 



Rocks, all subject to alteration, 28, 34 ; 

 alteration accompanied by recrystallization, 

 34 ; alteration of, a passage from an un- 

 stable condition towards a more stable one, 

 125 ; association of, 28 ; banding of, no 

 proof of stratification, 72 ; basic eruptive, 

 of iron region, varieties of, 46 ; causes 

 of induration of, 125; determination of 

 age of, by lithological characters, 94 ; ge- 

 ological age, told microscopically, 73, 74 ; 



their history, 28 ; intrusive garnet-bear- 

 ing actinolite probably altered andesites 

 and basalts, 49 ; intrusive, of iron district, 

 70 ; the microscopic study of, 73, 74 ; 

 mode of determining origin of, 08; names 

 given to local modifications of, 55 ; origi- 

 nal characters of, lost, 34; passage of dif- 

 ferent forms into one another, 40, 69 ; 

 requirements for study of altered forms, 

 74 ; resemblance docs not prove identity, 

 27, 28 ; sedimentary origin of eruptive, 

 11, 12 ; superficial study of, 09. 



Rocks, crystalline, origin of, 14, 15 ; passage 

 of different forms into one another, 4, 5, 

 14, 27, 37, 09 ; pre-PalcCozoic age of, 5. 



Rocks, eruptive, cryctallization of, 72 ; of 

 iron district, originally basalts, 46. 



Rock structures, origin of, 28. 



Rogers, II. D., copper-bearing rocks semi- 

 fused materials, 83 ; on the copper de- 

 posits, 82, 83 ; crystalline rocks of Choc- 

 olate and Carp Rivers of Primal or Pots- 

 dam age, 4 ; New Red age of Keweenaw 

 Point sandstone, 83. 



Roicers, W. B., Potsdam age of sandstone, 

 93. 



Rottcrmund, Count dc, report of, 91, 92. 



Ruiisles, D., on the origin of copper veins, 

 SO. 



St. Mary's River, sandstone of, 77. 



Salisbury Mine, geological structure of, 50 ; 

 " soft hematite " of, 49, 50. 



Salt cubes, in granite, 25 ; in quartz, char- 

 acteristic of Huronian granite, 56. 



Sand, concretions of, in shale, 121. 



Sandstone, action of trap on, 82 ; composed 

 of trachytic and rhyolitic material, 114, 

 115, 117, 119, 120; contact with quartz- 

 ite, 22, 23 ; containing trappean detritus, 

 110, HI; curved stratification of, 63; 

 formed of granite detritus, 60 ; formed 

 from volcanic debris, 117, 118; impreg- 

 nated with iron ore, 32 ; microscopic 

 study of indurated, 114, 115; origin of, 

 122, 128 ; precipitation of copper in, by 

 organic matter, 94, 95, 109 ; pebbles of 

 quartzitc in, 113 ; its relation to Presque 

 Isle peridotitc, 03, 64 ; its relation to the 

 traps, 109-113, 118 ; ripple-marks in, 

 79 ; stalactites of, 118 ; thermal water 

 action on, 03, 117; Torch Lake quarry 

 of, 117 ; on western side of copper-bear- 

 ing rocks, 120, 121, 122; microscopic 

 study of feldspathic, 60. 



Sandstone, Eastern, dip of, 113-119 ; geo- 

 logical age of, 122 ; relation to traps, 

 108; vountrer than the copper- bcarins; 

 rocks, 98, 99. 



