Manganese crust is a type of deposit that crystallizes out of seawater. In this picture, a rock has first been altered by contact with seawater (the yellow margin) and then covered in a black manganese rind.

Manganese crust is a type of deposit that crystallizes out of seawater. In this picture, a rock has first been altered by contact with seawater (the yellow margin) and then covered in a black manganese rind. Image courtesy of the OSU Argon Geochronology Lab.

 

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