When a protolith composed of clay and quartz is subjected to intense pressures and temperatures during a mountain-building event, the rock no longer contains clay and quartz, but instead, garnet and mica. The rock experiences metamorphism which is also is called neo-crystallization
The slow emergence of a new crystal layer on a rock is called neo-crystallization and it differentiates from the protolith.
The process "Protolith" indicates the old, original, and un-metamorphic rock that undergoes transformation and changes completely into a new metamorphic rock after a chemical reaction which wears away the old layers of rocks and new layers are formed having minerals and crystals.
In general, neo-crystallization is a time taking process that alters the older rocks and produces new minerals and crystals.
For example, limestone undergoes a phase transformation process or metamorphic process and gradually changes into marble.
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