182 THE VERMILION IRON-BEARING DISTRICT. 



The hematite, besides being interbanded with the other materials, also 

 occurs very frequently in masses of variable size and shape. These consti- 

 tute the ore deposits of the district, and will be considered under a separate 

 head. The bands are not arranged in any definite order, but alternate with 

 one another, giving a very regular ribbon or banded structure. All the 

 colored cherts have the white as a base, the difference in color being due 

 chiefly to the presence of the iron, either in the form of magnetite, hematite, 

 or limonite, or as a combination of these. The black cherts, frequently 

 called black jasper or hungr}^ jasper, always contain a large quantity of 

 magnetite, to which they owe their color. The brilliant- red jasper owes its 

 color, as is well known, to the thin transparent plates and minute specks 

 of blood-red hematite. The color of the brown cherts is due to the limonite. 

 The colors of the other varieties — gray, brown, and ocherous yellow — depend 

 on the mixtures of the above oxides or of their alteration pi'oducts. Of 

 somewhat rarer occurrence is the slightlj^ greenish and grayish chert, which, 

 although subordinate in quantity, is important in reference to the genesis 

 of the iron-bearing formation. This chert contains a considerable amount 

 of iron carbonate and griinerite, to which it owes its color. These chert 

 bands become yellow and brown on weathering, on account of the for- 

 mation of ocher by the decomposition of the carbonate and griinerite. The 

 hematite and magnetite bands associated with the cherts are very rarely 

 pure. On examining them it will be found in almost every case that the 

 hematite bands contain varying percentages of magnetite, and vice versa. 

 With these of course one is always sure to find a variable quantity of 

 quartz. Iron pyrite is mixed with these various rocks in small amounts, 

 but it is not known to occur in large quantity in this district. 



The most intimate relationship exists between the various above- 

 mentioned members of the iron-bearing formation proper. Gradual transi- 

 tion from one into another may be traced. Near the west end of Tower 

 Hill, in following the strike of the rocks, one finds the jasper becoming less 

 brilliantly colored and grading with continuous exposures into the black 

 magnetitic jasper. The iron formation has been folded, and as a consequence 

 is traversed by more or less frequent fractures. These fractures have been 

 filled by veins of quartz which run transverse to the banding in the iron 

 formation. The smaller cracks have very commonly been filled by iron 

 oxide that is in all respects identical with that occurring interbanded with 



