The last working underground mine in New Jersey, closed in 1986 and reopened as a museum in 1990, and the reason this corner of Sussex County is a pilgrimage for mineral people. The Franklin and Sterling Hill district has produced more than 360 different minerals, and NINETY-ONE of them fluoresce, which is why the underground rainbow room stops people in their tracks. The tour is a 1,300-foot walk on level ground through the upper workings; the mine below runs 35 miles of tunnel and over 2,600 feet deep, and those lower levels are flooded and gone. PUBLIC museum tour, Ogdensburg, New Jersey.
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