Both pink prehnite and thomsonite occur in amygdales in volcanic rocks of Keweenawan age in the Lake Superior region. Although the pink prehnite superficially resembles thomsonite, it does not develop the spectacular patterns with colour variations of gem quality thomsonite. The pink prehnite has long been misidentified and a history of this problem is presented. The pink colour of the prehnite is caused by internal reflections from very fine and evenly disseminated inclusions of native copper. (Preceding abstracts)-R.S.M.
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Pink prehnite from Michigan: a mineral much confused.