NJDEP - NJGS - IC - Graphite Deposits in the New Jersey ...
graphite mine in the State, ceased opera-tion about 1931. Graphite in the Highlands New Jersey graphite deposits and the rocks that host them in the Highlands are Precambrian in age. They are among the oldest rocks in the State and are about 1.2 billion years old. These rocks were meta-morphosed deep within the Earth's crust
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