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Crystal overgrowth involves the partial mantling of a mineral:
● by material of the same composition, or
● by material of the same mineral species but different solid-solution composition, or
● by an unrelated mineral.

Overgrowth implies crystallographic continuity between the two participating minerals so far as permitted by their differing crystal structures. Where the overgrowth forms a more or less continuous rim around enclosed mineral, it is termed a mantle.

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