i 



>,^ ^ _ ^L^ B^ V^U - 



Vlll 



INDEX. 



Newbcny, J. S., on tlxc origin of iron ores, 



23, U. 



Norian, in Eastern Massacliusctts, 72 ; erup- 

 tive basaltic; (t^Jibljro) foi'nis, 73. 



North Island, diabase and diorite of, 39. 



Nova Scotia, ti'ap of, 81. 



r 



Oltvink, action of magma on, 40 ; altera- 

 tion of, 42,61; in diabase, 40,42,43, 

 45 ; foreign in basalt, 119 ; gi-eenisli 

 . pseudomorpbs of, 01; in pevidolite, 00, 

 61 ; presence of, in iron region, 75 ; pscu- 

 domorjdis aller, 30. 



Ontonagon district, structure of, 104, 105. 



Ontonagon River, origin of cop^icr of, 70 ; 

 sandstone on west Ibrk of, 100. 



Organic nnitter, j)rccipitation of the enpp(^- 

 by, 92, 95, 109, 130. _ _ 



Ortlioflasc, secondary oi'igin of, 37. 



Osceola Mine, microscopic study of pebbles 



from, 119. 

 Ottrelite, microscopic characters of, 45. 

 Ottrebte schist, fornuLiion of, 30, 75; ml- 



CJ'oscopie study of, 45; prodn(;tion of, 45. 

 Ovifak, Dislco, iron-bearing basalt of, 13. 

 Owen, D. J)., on the age of the sandstone, 



84, 90. 

 Owl Creek Vein, mass copper of, 130. 



Valawaoic age of rocks of Eastern Massa- 

 chusetts, 72. 

 Palmer Mine, eruptive eliaracter of jasper 



at, 32. 



Peck, Samuel, credited with first discovery 

 of iron ore in the ii'on district, 4. 



Pendill Mine, geological structure of, 51. 



Penokee Gap, nnconformability of liuronian 

 and Laureutiau at, 25; liuronian and 

 Laurcntiau at, 24. 



Pcridotite, alteration of, 01-00; contnct 

 with sandstone, 2, 3 ; eruptive origin of, 

 64; place of, in lithological nomenclature, 

 05; of Ishpeming, 05, 00; of Presque 

 Isle, 2, 3, 42, 00-05, 75; microscoj)ie 

 study of, from Pj-cstpic l^lc, 00-02 ; rc- 

 latio'ns of, to sandstone at Prcstpte Pdi:, 



10. 



Permian age of copper-bearing rocks, 97. 

 Pctherick Mine, ''ash-bed" at, 112. 

 Phoenix (obi) Mine, "ash-bed" at, 112; 



diabase of. 111 ; a fissure vein, 129. 

 Picnic Island, diorites of, 23, 39. 

 Picnic Point, granite of, 39, 55, 50 ; micfo- 



scopie study ol" rocks ol', 39, ^'0 ; rocks (;1', 



39, 40, 74. 

 Pittsburg and Lake Snj)crior Mine, mu;ro- 



scopic section of iron ore intrusive in 



quartzite, 32. 

 Plagioclase, cutting augit-e, 42. 



Plasticity of iron ore, jasper, and chlorite 



schist,, 07. 

 Porcupine Mountains, geological structure 



of, 76, 77, 84. 

 Porodite, use of the tei'm, 00. 

 Porphyry, formation of, 84. 

 Portag(; Lake, copper deposits of, 94 ; dip 



of sandstone at, 82; melaphyr at, 94 ; old 



lava flows mined at, 124 ; trap at, 80. 

 Portage Lake district, eo])|)er deposits mined 



in, 128, 129; no iissurc veins in, 124; 



"sktes" of, 121. 

 Porter's Island, 80. 

 Potsdam age, of all Lake Superior rocks, 



12; of iron region, 20; of Keweenaw 



Point sandstone, 82, 84, 87, 90, 103, 



104. 



Potsdam sandstone, source of materials in, 

 00 ; microscopic study of, 00. 



rrchnite, igneous origin of, 80. 



Vni^i^mi Isle, dolomite of, 3; forming an 

 island in the Potsdam Sea, 23 ; geologi- 

 cal slruct;ure of, 2, 3, 9, 10, 23, 60 ; peri- 

 dotile of, 75 ; pcridotite and serpentine of, 



60-05. 

 Pseudo-arnvgdaloidal sirueture, origin of, 



100, 101,123, 129, 130. 



Pseudomorphs after olivine, 30. 



Pseudo-strati filiation, 28. 



Piimpelly, K., on alt.eration of basaltic rocks, 

 105; 'on black .inclusions in garnet, 47; 

 copper -hcai-ing ti'aps, diabases, and mela- 

 phyrs, 105 ; on Lhe deposition of the cop- 

 per by protoxide of iron, 97 ; derivation of 

 copper from sandaLone, 120, 1 27 ; geo- 

 logical rep(n-t on the copper distiact, 100; 

 pre-Potsdam age of coppev-bcaring rocks, 

 99; "specular slate ore," pseudomorph 

 after ehioi-ite schist, 20. 



Pyrite, in felsite, 3)8. 



QuAiiTZ, bearing fluid and vapor cavities, 

 38, 39. 114, 117, 119 ; containing double 

 pyramidal inclnslons, 120 ; crystals in 

 sandstone with unworn facets, 117; de- 

 vUrinration form of, 33 ; thiid inclu- 

 sions in, 43, 44, 45, 55; foreign, in 

 rhyolite and felsit,e, 119; grains formed 

 by fissuring of a silieious mass, 53, 54; 

 heat aciioji on, 33 ; indusions in, 44^ 

 54-59; microlites in, 38; prismatic 

 sti-ucture of surnmnding ring, 48 ; sec- 

 onibu'y origin of, 33, 30, 37, 38, 39, 47, 

 113, 114,117, 119, 120; stone cavities 

 in, 38, 119, 120; structure of, in fclsite, 

 118, 119; -witli unworn facets in saiid- 

 st;one, 60 ; water-deposited, 63. 



Quartz Porphyry, rhyolitie character of, 119. 



See felsile. 



