A secondary mineral or a random aggregate of secondary minerals (monomineralic or polymineralic) which have replaced an earlier mineral but have retained its shape. For example, a random aggregate of chlorite crystals which have replaced a euhedral augite crystal while preserving its shape is said to form a monomineralic pseudomorph of augite. Other examples include quartz after fluorite, serpentine after olivine, and limonite after pyrite, where the original cubic form is preserved. See also metasomatism.
Subjects: Earth Sciences and Geography.