Identifier: annualreport190401onta (find matches)
Title: Annual report
Year: 1891 (1890s)
Authors: Ontario. Dept. of Mines
Subjects: Mines and mineral resources
Publisher: Toronto
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: University of Toronto

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ningnumerous geodes of quartz crystal andveinlets of specular hematite. It issometimes botryoidal and even stalag-mitic. Under the microscope a fairly freshspecimen of ferruginous limestone isseen to consist of a mosaic of grains ofcarbonate more or less oxidized with theformation of hydrous iron oxides, andcontaining a few areas of chalcedonicsilica. The amount of iron carbonatecontained in the limestone is vari-able from place to place, but it some-times contains so much of this materialthat it might almost be spoken of as asomewhat oxidized siderite. Again, inplaces the rock has been greatly silici-fied, by the dissolution of the calcium,and magnesium carbonate, by the actionof waters containing carbon dioxide, andwith the deposition of silica in theirplace. Its iron carbonate has been en-tirely oxidized to hydrous iron oxide,and has been added to by the infiltrationof further iron oxide formed by the oxi-dation of superior iron carbonate in fer-ruginous limestone, now entirely re-
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(151) 152 Bureau of Mines No. 5 moved by the glacial erosion and byother means. These enriched masses oc-cur at intervals throughout the beds,but apparently are more frequent to-wards the centre of the deposit and atlower horizons. It was observedthat the carbonates immediately over-lying the inferior gneiss wererichly ferruginous. At the outcropthe iron-bearing rocks are never suffi-ciently rich to be termed iron ore, butworkable bodies of this valuable ma-terial may exist at short distances inthe interior or beneath the surfacealong the river. The following an-alyses represent chemically the char-acter of the Opazatika iron-bearingrocks. tainly not less than that of thestream at the point (about 75yards), and that a minimum thicknessmay be set at fifteen feet ana is pos-sibly greater, it will appear to be afair-sized bed and one in which work-able bodies of iron ore may possibly befound. As the carbonate contained nomagnetite, we could not trace its con-tinuation towards the interio

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