PETROGEAPHIGAL CHARACTER OF NEGAUNEE FORMATION. 363 



lu the folding of the rock the readjustment has occurred mainly in the 

 iron oxide between the jasper bands. As a result of this, the iron oxide has 

 been sheared, and when a specimen is cleaved along a layer, it presents a 

 brilliant micaceous appearance,- and such ore has been called micaceous 

 hematite. This sheared lustrous hematite, present as some form of iron 

 oxide before the dynamic movement, is discriminated with the naked eye or 

 with the lens from the later crystal-outlined hematite and magnetite which 

 fills the cracks in the jasper bands and the spaces between the sheared 

 laminae of hematite. The jaspilite differs mainly from the ferruginous chert, 

 with which it is closely associated, in that the siliceous bands of the former 

 are stained a bright red by hematite, and the bands of ore between them 

 are mainly specular hematite, while in the cherts the iron oxide is earthy 

 hematite. The jaspiUte in its typical form, whenever present, always occu- 

 pies one horizon — the present top of the iron-bearing formation, just below 

 the Goodrich quartzite. In different parts of the district it has a varying 

 thickness. With tliis jasper, or just above it, are the hard iron ores of the 

 district; hence it has been called "hard-ore jasper" l)y the miners, to 

 discriminate it from the ferruginous chert, or "soft-ore jasper." 



An analysis of one of the typical jaspilites, made by George Steiger, 

 in the laboratory of the Survey, is as follows : 



A nu h/sis of Jaf:}>iU/c. 



Soluble matter, chiefly iron oxide 

 Insoluble matter 



Total 



62.36 

 37.64 



The insoluble matter contains — 



SiO.2 



Al,03 



FejO, 



MgO 



Alkali oxides 



Total . 



98.91 

 .53 

 .40 

 .20 

 .10 



100. 14 



