178 THE CRYSTAL FALLS IRON-BEARING DISTRICT. 



holes it appears certain that the ore formation is immediately underlain and 

 overlain by black slates. The foot and hang-ing- slates are much alike, the 

 hanging, however, being very pyrltiferous, and the foot containing much 

 more iron than the hanging. This iron is in the form of hematite and mag- 

 netite. Below the black magnetic slate is the ferruginous mottled slate, 

 wliich apparently lies next to the Lower Huronian Hemlock volcanics. 

 The so-called ore formation consists of banded chert and jasper, with which 

 the hematite bodies are associated. 



The results obtained from these holes sliow the lenticular character of 

 tne ore bodies and the difficulty in finding them. One of the holes passed 

 through the ore formation, but missed the ore body, which subsequent 

 underground work showed it would have struck had it cut the formation 50 

 feet farther north. 



The distribution of the Huronian rocks in the vicinitj^ of Amasa is 

 shown on the map, PI. XVI. 



THE CRYSTAL PALLS AREA. 



The most of the observations upon the ore bodies and their relations to 

 surrounding beds have naturally been made in the vicinity of the town of 

 Crvstal Falls, where, owing to the extensive development of the mines, the 

 underground conditions could best be studied. The conclusions reached, 

 however, are confidently believed to hold good for the entire Upper Huro- 

 nian of the district. 



In the description of the folding of the Upper Huronian it was stated 

 that the Crystal Falls area is in a synclinorium forking as the result of a 

 subordinate central anticline so as to produce a U opening to the south of 

 west. It is in this basin that the important mines of the Crystal Falls dis- 

 trict are situated. One row of mines — the Hollister, Armenia, Lee Peck, 

 and Hope — as shown hj the map (PI. XVII), lies to the Avest and north- 

 west of the main mass of Hemlock volcanics between Crystal Falls and 

 Mansfield. A second and more important set of mines follows an east-west 

 line south of the subordinate area of volcanics, which lie just north of Crys- 

 tal Falls in the midst of the Upper Huronian sediments. The second set of 

 mines, including the Crystal Falls, Oreat Western, Lincoln, Paint River, 

 Lamont, Youngstown, and Claire, lies near the axis of the syncline — that 

 is, along the line of major folding, and consequently greatest mashing. The 



