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Darwin, trained by Sedgwick, noted the contact metamorphism between the former hot molten lava and the earlier cool limestone.

In the case of intense contact metamorphism, the altered rock assumes a new form, and may exhibit a crystalline and foliated or schistose structure.

The principal agencies which take part in contact metamorphism are heat, heated waters, pressure, and perhaps movements within the rocks.

The analogy between rocks altered by contact metamorphism and those affected by regional metamorphism had led to the conclusion that the latter, like the former, have been changed by heat and the passage through them of heated water bearing mineral matter, and especially silica, in solution.

The heat of an intruded magma affects the rocks it traverses and produces what is termed contact metamorphism.