Duke stone is a type of Carolina 'slate' or 'bluestone', a metamorphic phyllite rock, with both andesite and dacite mineral composition. Dacitic phyllite is a predominant type of rock found through the Carolina Slate Belt. Duke stone and the Carolina Slate Belt, like the greater Carolina Terrane, are thought to have formed in the Iapetus Ocean off the coast of Gondwana by a chain of volcanic islands known as 'Carolinia', starting around 650 million years ago.
Duke stone is a type of Carolina 'slate' or 'bluestone', a metamorphic phyllite rock, with both andesite and dacite mineral composition. Dacitic phyllite is a predominant type of rock found through the Carolina Slate Belt. Duke stone and the Carolina Slate Belt, like the greater Carolina Terrane, are thought to have formed in the Iapetus Ocean off the coast of Gondwana by a chain of volcanic islands known as 'Carolinia', starting around 650 million years ago.