390 E. C. HARDER AND R. T. CHAMBERLIN 



micaceous texture. It consists mainly of soft hematite in which 

 quartz occurs in varying abundance together with talc, kaolin, 

 mica, and earthy pyrolusite and frequently tourmaline. Presum- 

 ably the term as used by Hussak includes those portions of the iron 

 formation which have been affected by gold-bearing solutions, and 

 it seems best to limit its use in the future to this phase and to avoid 

 its use in the iron-ore terminology. 



The bedded ores of the third class, the laminated, are distinct 

 from those of the other classes and more closely resemble the ita- 

 birite in texture. These ores might be termed itabirite with little 

 or no quartz sand. They occur in large lens-like deposits in the iron 

 formation, as do the hard ores and soft ores, but the boundary 

 between one of these lenses and the itabirite of the iron formation 

 which incloses it is less well defined and more irregular. While 

 the hard ore and soft ore deposits generally have a sharp contact 

 with the inclosing itabirite, the laminated ore deposits generally 

 have a zone of gradation with the itabirite and also have inter- 

 bedded masses of itabirite within them. The separation of ita- 

 birite from laminated ore is frequently quite arbitrary, being 

 controlled by the percentage of metallic iron. 



Lenses of hard ore or soft powdery ore occur interbedded 

 within laminated ore deposits in the same way that they occur in 

 the itabirite portions of the iron formation. In such cases the 

 contact with the hard ore is well defined, but that with the soft 

 ore less so. 



Laminated ore is a very thinly bedded, porous ore which is quite 

 friable, breaking into thin plates along bedding planes, owing to 

 the fact that the porosity is concentrated along these planes. 

 The ore is red or blue hematite, much of it in the amorphous 

 form, with a considerable percentage of limonite. The different 

 varieties of laminated ore are generally found interbedded or inter- 

 laminated. Certain beds may be red, others blue, and still others 

 yellow, the differences being the result of hydration and slight 

 admixtures of clay and other impurities. Frequently siliceous beds 

 of different thicknesses will be found interbedded with pure ore. 



The laminated ore is not so high in grade as the hard ore and 

 soft ore, for the metallic iron content of its richer portions varies 



