The Milldale Limestone in which the cave is located is a type of limestone known as ‘Reef Limestone’ and is made from the remains of corals, crinoids, and shells.
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This cave like the others in this area is formed by ‘acid rain’ as limestone is not soluble in pure water. Rainwater absorbs carbon dioxide and becomes slightly acidic allowing it to react with the solid calcium carbonate, limestone, to form a calcium bicarbonate solution.