Franklinite with Calcite, Willemite

specimen number:
2072163

location:
Franklin, Sussex Co., New Jersey, USA

description:
A classic fluorescence specimen from this famous locality. Massive calcite with grains of franklinite and willemite throughout. The photo was taken with shortwave ultraviolet light. The video shows the specimen in normal daylight.

The Franklin mining district in Sussex County, New Jersey, is globally recognized as the fluorescent mineral capital of the world due to its extraordinary mineral diversity. Geologically, the deposit is a unique Precambrian-aged zinc-iron-manganese ore body hosted within the Franklin Marble, formed through complex metamorphic processes acting on ancient seafloor sediments. The primary ore minerals, franklinite, willemite, and zincite, are found in few other places in such massive concentrations. Historically, mining in the area dates back to the mid-1700s, with large-scale industrial operations beginning in the 1800s under various companies that eventually consolidated into the New Jersey Zinc Company. The most intensive period of operation occurred from the late 19th century until the final closure of the Franklin Mine in 1954, followed by the nearby Sterling Hill Mine in 1986. Today, the site is a legendary destination for collectors, as the local minerals are famous for their brilliant, multi-colored fluorescence under ultraviolet light, a phenomenon caused by the specific manganese activators present in the ore.

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