Franklinite

specimen number:
2262120

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

description:
Crystals of franklinite to 2.2 cm in size throughout this massive calcite matrix. Some damage crystals present, the prominent crystal in good condition. Classic material for this New Jersey locality.

Franklin, New Jersey, is home to one of the most remarkable mineral deposits on Earth, situated within the Reading Prong of the Highlands physiographic province. Geologically, the ore body consists of a massive, hook-shaped lens of Precambrian metamorphic rock known as the Franklin Marble, which hosts a unique assemblage of zinc, manganese, and iron minerals. The site is the type locality for franklinite, a complex oxide mineral that occurs as black, metallic octahedral crystals and is virtually unique to this district and the nearby Sterling Hill mine. Historically, mining and quarrying began as early as the mid-17th century with local iron smelting, but industrial-scale zinc mining flourished from the mid-1800s following the consolidation of various interests into the New Jersey Zinc Company. The Franklin Mine operated continuously through the 19th and early 20th centuries until its deep-shaft operations were finally exhausted and closed in 1954. Despite the cessation of commercial mining, the locality remains a global destination for researchers and collectors due to its more than 350 identified mineral species and its famous fluorescent mineral specimens, with preservation efforts continuing through 2026 at the Franklin Mineral Museum.

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