Graphite

specimen number:
2102309

location:
High Bridge, Hunterdon Co., New Jersey, USA

description:
A bright lustrous solid mass of graphite from this old locality. Very nice for the species.

The High Bridge graphite deposit, located in Hunterdon County, New Jersey, is situated within the crystalline Highlands of the Reading Prong. Geologically, the graphite occurs as flakes and crystalline masses disseminated through Mesoproterozoic-age Franklin Marble and associated gneisses, formed by the regional metamorphism of carbon-rich sedimentary rocks. The mining and quarrying operations targeted these high-grade bands where graphite reached concentrations sufficient for industrial extraction. Historically, the most significant activity occurred at the High Bridge Graphite Mine, which was intermittently active from the late 19th century into the early 20th century. Production was particularly notable between 1890 and 1910, as the site was developed to supply material for crucibles and lubricants during the industrial expansion of the Northeast. While various companies attempted to modernize the milling and separation processes to handle the hard gneissic host rock, commercial viability proved difficult against cheaper foreign imports, leading to the eventual cessation of operations by the 1920s. Today, the remains of the mine and its waste piles are recognized by mineralogists for providing distinct specimens of crystalline graphite and associated silicate minerals characteristic of New Jersey's metamorphic geology.

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