Latitude: 41°3'46"N
Longitude: 74°34'19"W
Ref.: The Iron Mines of New Jersey (1910), Bayley:277-281; Anderson (1980); Dunn, P.J. (1995), Pt 1: 91. An iron mine in magnetite ore located 2 to 3 miles SE of Ogdensburg in Sparta Township. This mine was owned by the New Jersey and Pennsylvania Concentrating Co., an enterprise of Thomas Alva Edison. Edison was a respected inventor of mining technology, including beneficiation machines. Here he applied his inventions to concentrate magnetite into briquette but almost went bankrupt when the Mesabee Range deposits were discovered in the mid-west. Workings here are a large open cut. This mine incorporated several of the earlier Ogden group mines.
The Edison Mine was developed in the 1890’s by Thomas Edison. Edison invested approximately $2 million of his own funds and another million of investor money. The idea was to mine relatively low grade iron ore, cheaply from surface open pits, concentrate the magnetite and form it into briquette heavy enough to be blast furnace feed. The mine site was chosen after an extensive dip needle (sort of a crude magnetometer) survey of zone that contained numerous small iron mines and exploration trenches. The small mines were opened on local, relatively high grade areas, within an extensive area of low grade magnetite-bearing rock. The most extensive tract of ore with an adequate grade for the project became the site of the Edison townsite, the mill and the two major ore producing quarries. The Edison mine workings were superimposed on some of the older mines, mainly the Ogden and Roberts.
The Edison mine was a large industrial enterprise even by today’s standards. Because it was remote from the established towns, by the standards of the time, it included housing for the workers and was the first populated place in the area with electricity and electric lights. Because there was a railroad spur to the site it became a tourist destination because it combined the scenery of the hills and forest with the industrial progress that was so highly valued in that era.
The Edison mine exploits a type of ore that is unlike that of most of the great many iron mines that doted the Reading Prong highlands of New Jersey as well as adjacent New York and Pennsylvania. Magnetite was contained in a potassium feldspar gneiss. The magnetite-rich bands are concordant with the foliation of the gneiss indicating that it is a premetamorphic feature. The typical grade of this ore was 12 – 14% Fe. Although Kspar gneiss is a fairly common lithology in the northwestern highlands most has been interpreted as meta arkose. However, recent evidence ( Puffer and Gorring, Can. J. Earth Sci. 42(10): 1735–1748 (2005) ) suggests that the Kspar gneiss that hosts the Edison mine ore may be a meta rhyolite.
Ore at the Edison mine was extracted from 2 parallel bands of magnetite-rich gneiss, each approximately 40-50 feet thick and 50-75 feet apart. The most dramatic icon of these parallel bands is the Horseshoe cut with its 2 narrow, parallel cuts separated by a mass barren material. Another interesting aspect of the ore deposit worked by the Edison mine is a sulphide-rich horizon. The sulphide horizon ranges up to 40 feet thick and contains elevated concentrations of pyrite, pyrrhotite, chalcopyrite and molybdenite. It is adjacent to or overlaps the southeastern magnetite ore band and extends thru the Horseshoe and Roberts cuts. In the Horseshoe cut the sulphide horizon was intruded by pegmatite and recrystallized. The recrystallized areas produced some very fine molybdenite crystals.
Just northeast of the Roberts cut the Kspar gneiss band is split by a fold. The sulphide horizon reappears in the eastern branch of the Kspar gneiss band. Approximately 3000 feet northeast of the northeastern end of the Roberts cut is the “Copper shaft”, an exploration in a portion of the sulphide zone containing significant bornite.
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