The Hoit Mine, in
Oxford Township, was opened about 1870 by means of a slope, into an outcrop of
ore, initially dipping 30 degrees to the southeast. Although there are no
records as to when it was closed, Bayley places its abandonment around 1875 (Bayley,
259). As is common with magnetite deposits in the Highlands, the dip of the vein
increases with depth. Hence, the slope becomes steeper towards the bottom of the
mine, gradually disappearing beneath the water table.
The deposit was eventually drifted upon at right angles to the slope, for a distance of about seventy feet. Bayley attributes this to the ore-body being irregular at this point, possibly “due to an anticlinal fold, or to a throw of the vein westward (Bayley, 259).” Southeast of this drift, evidence of workings exist. Remarkably, this stope gives the singular impression of a room-and-pillar mining operation; with several evenly spaced pillars of ore left in place to support the roof.
Although the water table was unusually low on our last inspection of the mine, we were not able to ascertain whether these workings extend beneath the water table. Our preliminary observations would suggest that, if they do, they do not continue for any great distance. At any rate, a more thorough examination in the future, including soundings, would shed more light on this mystery as the historical descriptions are vague.
Beyond these workings, the drift continues another fifteen or twenty feet before ending in what appears to be a flooded winze filled with timbers and other refuse. We were not able to establish the exact depth of this feature beyond twelve to fifteen feet. Whether this “winze” was driven merely as an exploration, or if it once connected with a lower level of the mine, is not known. Without a more complete historical description, or a severe drought to make exploration possible, the answer to this question remains one of pure conjecture.
From measurements taken of the workings previously described, with the understanding that most of them were driven in ore, we would estimate the production of this mine at between twenty to twenty five thousand tons. This estimate is made under the assumption that a majority of the material raised was ore, and without respect to what may lie beneath the water table. Actual production figures for Hoit mine are not listed in any of the geological reports.
The Hoit mine is peculiar for several geological anomalies. Apart from the irregular behavior of the deposit already described, the ore contains a fair amount of garnet, a condition which Bayley describes as being “rare in the New Jersey magnetites (Bayley, 260).” Bayley completes his description of the Hoit mine by stating that: “The associated rocks are also abnormal. Instead of the usual gneiss of the district, the rock forming the walls of the ore body is a much sheared garnetiferous quartzose schist, containing a considerable quantity of garnet and some sillimanite. It may represent an old sediment that has been metamorphosed by the surrounding gneisses (Bayley, 260).
-Hoit Mine Write up courtesy of Frank Meloi.
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