Huff Mine (Hoff Mine), Dover, Morris County, New Jersey, USAi

Regional Level Types
Huff Mine (Hoff Mine)	Mine
Dover	Town
Morris County	County
New Jersey	State
USA	Country

HUFF MINE (25)

The Huff (or Hoff) mine is on the east slope of the hill northwest of Washington Forge pond. The main shaft (fig. 32) is about 50 yards west of the Wharton-Spicertown road. The mine was worked intermittently from the time of its opening prior to 1855 until it was abandoned about 1911. Between 1855 and 1868 it was worked to a depth of 150 feet and along a length of approximately 600 feet, yielding about 50,000 tons of ore. By 1880 it, had produced 78,000 tons of iron ore. The mine was in operation for short periods during the 1880's; it was abandoned in 1886, at which time the mine was 200 feet deep and presumably had reached bottomrock. It was reopened in 1905 by the Ifoff Mining and Realty Improvement, Co. of Rockaway. The shaft was sunk a few feet deeper and the ore was found again. The supposed bottomrock was only a pinch in the ore. The mine was operated on a small scale until it was closed. During the period immediately preceding its closing about 12,000 tons of ore was hoisted annually.

The principal workings that were accessible in 1911 are shown on figure 31. The shaft is inclined 45° SE. and connects with the first and second levels. An inclined bucket slide connects with the third level. A dip-needle map of part of the surface is shown on figure 32. The maximum attraction lies over the East vein. Reconnaissance dip-needle traverses indicate that this belt of positive attraction is about. 1,200 feet long.

There are two nearly continuous series of pits at the surface. The interval between the line of pits is about 150 feet near the southwest end, but it is only about 75 feet near the shaft. The pits probably represent the surface workings on the two main deposits, the West and East veins. The main shaft is on the East vein. The East vein dips 63° SE. at the surface. Grooves on the walls plunge 19° NE. The West vein dips about 70° SE. The open stopes indicate that the deposits are narrow and rarely exceed 8 feet in width. The host, rock for the ore is oligoclase-quartz-biotite gneiss. The gneiss also forms the wall rocks and usually contains several percent, of disseminated magnetite. The magnetite occurs as thin laminae, from a fraction of an inch to about 1 foot in width, which alternate with layers of gneiss that
contain some disseminated magnetite.

According to Bayley (1910, p. 369) the ore forms a series of shoots that dip about 60° SE. and rake 35° NE. In the mine workings two deposits from 10 to 14 feet apart were worked. The West (footwall) "vein" averaged 9 feet in width; the East "vein,'' 6 feet. The rock layer separating the two deposits was noted to thin with depth. The ore mined in 1886 averaged 45 percent Fe. An analysis of a carefully selected sample taken from the bottom of the mine in 1880 gave: 54.19 percent, Fe, 1.33 percent P, and a trace of S
(Cook, 1880, p. 106).

The Huff deposits are, about 1,000 feet northwest of the Mount Pleasant ore body. The Dolan and Scrub Oaks deposits are similarly situated in relation to the main deposits in the Wharton ore zone, but there is no evidence of a continuous linear mineralized belt between the Huff and these deposits.