It was dusty and noisy down in the mine shaft. The day shift had been working for hours with picks and shovels. It was dirty, backbreaking work and the men were tired. Suddenly the crude electric lights flickered. The knife switch shorted and sparked. Some were frightened, some prayed- all looked with awe at the erie glow of rainbow colors that suddenly surrounded them...colors emitted by the rocks around them.
Miners accidentally stumbled upon fluorescent minerals near the end of the 19th Century, when the light of emitted sparks from poor connections on electrical contacts emitted ultraviolet light, revealing the fluorescent quality of the minerals. And in the highlands of New Jersey, in Sussex County, miners worked the two most extraordinary mineral deposits on the planet.
Approximately 10 percent of all the mineral species known in nature occur in the Franklin and Sterling Hill mining district of Sussex County. In this one area, a number of world records are held:
- 345 species of minerals known in nature occur here.
- 35 species of minerals found nowhere else in the world.
- 84 species fluoresce under ultraviolet light.
- 69 new mineral species have been initially discovered from these deposits.
This area is famous for its zinc deposits. They were immense, easily worked and exceedingly rich. The Mine Hill deposit in Franklin eventually yielded 22 million tons of zinc ore, and the Sterling Hill deposit in Ogdensburg yielded 11 million tons! The ores were mined principally for zinc metal, of which about 6 million tons was recovered - enough to galvanize every roof in the United States and Canada!.
This ore consisted of the minerals zincite, a zinc oxide, willemite, a zinc silicate and franklinite, a zinc iron manganese oxide. These three principal zinc-ore minerals are practically unique individually and in the combination, and serve to set these deposits apart - there are no other zinc deposits on Earth like these.
Both of these intimately related ore deposits are of great interest to science. After 180 years of scientific investigation, the characterization of over 345 minerals and the publication of more than 1,000 papers, reports and monographs, their origins are still shrouded in mystery.