Sulphur Hill Mine (Sulfur Hill Mine), Andover Township, Sussex Co., New Jersey, USA

Ref.: Dana 6: 1065; The Iron Mines of New Jersey (1910), Bayley: 11, 220-223; NJ State Geol. Annual Rpts.: (1855): 152; (1868): 642-647; (1873): 88; (1879): 86-87; (1880): 118-177; (1883): 145; Dunn, P.J. (1995), Pt 1: 89; Pinger (1941, 1946; Sims & Leonard (1952); Pustay & Shea (1982). An iron mine in magnetite ore located approx. 1½ miles NNE of Andover. Operated 1855-1863 (?) and intermittently 1871-1880. Closed in 1883. Workings feature a pit 65 to 75 feet deep, 30 feet wide and 100 feet long. This mine is famous for its variety of minerals and as the "other" willemite locality in New Jersey (unrelated to the Franklin zinc orebodies).

The Sulphur Hill Mine is centered on a small lens of impure calcite-pyroxene marble and diopsidite. Within the Sulphur Hill pit the marble also contains large amounts of the vanadian garnet, goldmanite (Volkert and Puffer, 2001), plus magnetite and sulphide minerals, which made processing the ore difficult. Pyrrhotite was the most abundant sulphide along with lesser pyrite and chalcopyrite. Sphalerite and galena, mostly argentiferous, were locally abundant. Small amounts of molybdenite were also present. A rough assay, done in the mid 1970, using galena separated from the skarn, yielded an estimate of 35 oz. of Ag/ton of galena. Several pounds of galena yielded a silver bead about the size of a 00 buckshot pellet.

Willemite was first reported from Andover by Kitchell (1855). The original description of the material mentions an association with well crystallized garnet and states that the willemite was found in cavities “among the garnet crystals”. There is also mention of ocherous, black manganese oxides in some abundance. This description leaves no doubt that the Sulphur Hill Mine was the source of the willemite. The description was written in the year that the Sulphur Hill Mine reportedly began development so it can be safely assumed that it was found in a near surface concentration of sulphide that had been oxidized.

It should also be noted that another, entirely separate occurrence of willemite was discovered, approximately 113 years later, in the nearby Andover Iron Mine. This occurrence, in a quartz-calcite-sulphide vein, was also due to the oxidation of sphalerite

References:
Kitchel, w., 1855, Second annual report of the geological survey of the State of New Jersey, for the year 1855.

Volkert, R.A., and Puffer, J.H., 2001, Field trip day five. Road log for the Sulphur Hill and Andover Iron Mines, New Jersey, in Slack, J.F, ed., Part 1. Protorozoic iron and zinc deposits of the Adirondack Mountains of New York and the New Jersey highlands, Soc. of Econ. Geologists Guidebook Series, V. 35, pg. 99-101.