All the ore produced by the mine came from the Greenside Vein, a mineral vein which filled a geological fault running in a north-south direction through the east ridge of Green Side, a mountain in the Helvellyn range. Mining activities traced this fault for a length of and to a depth of . Four areas of the vein, known as ore shoots, contained galena, an ore of lead which also contained small amounts of silver. At first the ore was mined simply by driving adits into the mountain-side. To access ore at greater depths, two longer levels were driven from lower down but further away, and then a series of shafts were sunk within the mine. The lowest point in the mine was roughly 100 m below sea level, where the surrounding andesite rock rested upon underlying shales in which the fault had not been mineralised.