296 J. P. Kimball on Iron Ores of Marquette, Michigan. 
ronian series in the vicinity of Marquette, are in reality indigen- 
ous greenstone, and a portion of the development of the diorite 
upon which repose the upper members of the series, and which, 
as will hereafter be shown, is uncovered along most of the ridges 
of the region. No instances of trappean overflows in this region 
have been brought to notice. Quartz veins, sometimes carrying 
the sulphurets of copper, lead, and iron, are of frequent occur 
rence, occupying fissures evidently of an extensive vertical 
range. Workable veins of copper pyrites have recently been 
discovered. This is another point of agreement between the 
features of the Huronian series as developed in this district, and 
upon the north shore of Lake Huron, where eopper-bearin 
veins are frequent, of which those of the Bruce, Wellington 
Wallace mines are well known examples 
es. — 
It is urged by Prof. Rivot of Paris, that the crystalline and 
schistose rocks south of Keweenaw Bay entirely correspond ger 
int; for he asserts the syenite of 
tercalated greenstones, amygdaloids, sandstones and cong oe 
‘will be well to advert very briefly to certain remarkable a le 
ceptions upon which they are based. First: There seems 7 
* Foster & Whitney’s Re ort, ii, 44, : 
* Rivot, Notice he Aes Deciid oie. Maleate des Annales des Mines, % P: e 
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