I40 NEW YORK STATE MUSEUM 



In approaching the mines from Oswegatchie, the highway after 

 leaving the Oswegatchie river at Fine passes over a belt of horn- 

 blendic and micaceous gneisses and schists that continues for a 

 mile or more and is then succeeded by a red granitic gneiss with 

 porphyritic feldspars. This rock prevails in most of the exposures 

 as far as Monterey. Between that locality and the Clifton mines 

 the granitic gneiss gives way to a belt of schists and limestones 

 having a northeast-southwest trend parallel to their general strike. 

 These are the predominant rocks in the vicinity of the ore bodies. 

 They seem to have been somewhat broken and disturbed as they 

 show sudden changes in dip; the inclination, however, in most 

 cases is toward the southeast at angles of 15° to 45 . 



The openings are located on the sides and summit of a hill rising 

 100 feet or a little more above the site of the steel works in the 

 adjoining valley. The principal working is an open cut on the 

 summit which exposes a vein 20 feet wide for a distance of about 

 500 feet. This is known as the Dodge vein. The immediate wall 

 rock is a hornblende schist. Bands and fragments of the schist 

 interleave the ore, and on the borders the two are intimately mixed. 

 The hornblende gangue carrying the magnetite makes an exceed- 

 ingly tough material. On the northeast side of the hill the vein 

 has been tapped by an adit and in the walls crystalline limestone 

 is exposed in what seems to be an included band about 5 feet thick. 

 The southwest continuation of the vein has been explored by a 

 shaft that follows the dip for 30 feet, showing about 20 feet of ore 

 all the way. East of this deposit and higher up in the schists is the 

 St Lawrence vein, 8 feet thick, that has been explored by open 

 cutting and by an incline said to be 100 feet deep. The ore from 

 it is very sulfurous, in places almost solid pyrite and pyrrhotite. 

 A third vein is known to underlie the Dodge vein, but its width 

 and character have not been determined. 



The ore found in the different openings varies from a coarse 

 and nearly pure magnetite to a fine grained mixture of disseminated 

 magnetite and the minerals of the wall rock which are chiefly horn- 

 blende, biotite, garnet and quartz. Pyrite is less in evidence in 

 the middle of the veins than on the borders. The ore was subjected 

 to heap roasting before it was smelted to reduce the sulfur. The 

 analyses that follow are quoted from a paper on the Clifton mines 

 by Professor Silliman. 1 



'Am. Inst. Min. Eng. Trans. 1871-72. 1:364. 



