Plate XXVII.— JASPILITE, AND ORE AND JASPER COXGLOMERATE. 



Fig. 1. Jaspilite from the Jackson mine, Negauuee (Atlas .Sheet XXVIII). This figure represents a 

 typical piece of the regularly banded jaspilite. The bluish-gray bands are brilliant specular 

 hematite. In the red bands each granule of quartz contains innumerable particles of trans- 

 lucent blood-red hematite. The lenticular character of the jasper bands is well illustrated, 

 the specimen being selected especially to show this. The transverse fracturing of the jasper 

 and other bands and the secondary infiltration of iron oxides are shown. 



Fig. 2. Ore and jasper conglomerate from Saginaw range (Atlas Sheet XXVI). This is a typical 

 basal conglomerate of the Goodricli quartzite of the Upper Marquette series. The detritus 

 consists almost wholly of various materials derived from the Negaunee formation, including 

 jasper, chert, aud ore. There is present, however, some quartz derived from the Archean. 

 A close examination of the illustration shows that secondary hematite and magnetite have 

 largely formed in the spaces between the grains about many of the jasper fragments, and, 

 indeed, have partly replaced the jasper fragments themselves. This is beautifully shown 

 at the lower left-hand corner of the figure. In those places where the basal conglomerate 

 is fine-grained these replacements by iron oxide may be almost complete, in which case an 

 iron-ore deposit is formed. Of such an origin is the iron ore of the Volunteer and some 

 other mines. 

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