Coppermine Brook, rises in South Mountain Pass. It then flows in a generally northern direction and passes under Route 9D. Here it’s seen as it passes under Mystery Point Road from where it continues its course until it flows into the Hudson River. I’m not entirely sure to which mine this refers, but it seems likely that it’s the Manitou Copper Mine. According to NY-NJ-CT Botany Online site :

The Manitou Copper Mine was opened about 1767 by Peter Hasenclver (see Ringwood Manor State Park in New Jersey). The iron mining operation was not successful because the ore was too sulfurous. The extensive dumps of the old mine are found on the east end of the ridge of Anthony’s Nose.