THE IRON-BEARING MEMBER. 275 



opment of the deposits wliicli were uriiiiually tuimd at the surface has 

 carried them, in f^very case iu which they are of any magnitude, below 

 the surface of the c<iuntry rock. A practical result <it' this is that many 

 mines whicli hegan as open jiits, continued tlieir workings as underground 

 mines as developments went on. Botli of these facts, the tracing of the 

 deposits of ore discovered at depths to the surface and (hosi; discovered at 

 surface beneath rock, are inevitable deductions from what has preceded as 

 to the position of the ore witli reference to the underlying foot-wall rock 

 and dikes. It also follows from tlie aljove that an ore <le|)osit upon one 

 property will pass, sooner or later, upon an adjoining propert\ ; so that sev- 

 eral deposits of ore, one al)ove the other, each bottomed by dikes, will l)e 

 found at a certain 2>lace among a row of nnnes, provided that the deposits 

 continue to a sufficient depth. ^ 



Rock above the ore. — The rocks which are found above the ore deposits 

 are the ferruginous cherts, the rocks whicli have been spoken of as the 

 characteristic ones near the Inise of the Iron-bearing meiiilier throughout 

 the area in Avliich the ores occur. The u])])er l)oundar\ of the deposits 

 differs from the quartzite and dike boundaries in that the change froui 

 ore to the clierty rock is a gradual transition instead of an al)ruj)t one. 

 In passing upward through an ore deposit, as its border is icached, the ore 

 becomes mixed with chert imtil so poor in iron as to become unsalable, 

 although perliaps carrying 50 })er cent or more of metallic iidu. In pass- 

 ing still farther upwards, the amount of chert liecomes greater, luitil a 



' Already (July, 1890) the Asblaiul iiiiiio, at the west end of the property, has {jouc through the 

 first hasemt'iit dike and a rimsidi'ialile thickness of ihert and ore and lias struck anotliir ore dipusit 

 presiimaldy lioOonii'il by a so<<iud dike. The first deposit ha.s heen developed ipiite to the east I'liil <d' 

 the projierty, so ttial tlic inaiiajters of the Norrie felt snri' of liiiiliiij^ the Ash hind deposit hy put tin;; 

 a shaft ilown throngli the husenieiit dike of the deposit l>efore known. This they have done with the, 

 antici]iated success. The .\uiora mine has at present fully develo]M d the ore deposit lyin;; on its 

 basement dike; so thai practically aU id' it may hi' s.-iid to lie in si;;ht. 'flicy must soon al(eiii|it to 

 find the Norrie deposit, f his w ill necessitate a shaft of very eonsideraldc depth, and will when tried 

 he an interesting experiment as thiowiiig li;;ht iii)on the dciith to which lar;ri' deposits may he 

 depciiilcd upon with sonic certainty to extend. The Colhy ilikc, of ureal size and at tirst oMrlain hy 

 a ;;reat dejiosit of ore. when followed to the east has heen found to break up. with a ciiiisci|iicnt, 

 breaking np and dimiiiiitioii of value of the ore deposit. 



The .Miiiiiit Hope niiiic has liccii s:iiil lohavca westward pitchiiii; dike; that of llic Aurora is 

 east; that of the I'ahst lid ween tlic t « n lias lit tic jiitcli. It is iicarl> certain that this is the same 

 great dike which iu the shape of a j;reat liall s.incer hoMs ihe ore deposits of these three mines. 



