The correct term to finish the statement is "metamorphosed."
Explanation:
1. When sandstone, which is the protolith (original rock), undergoes intense heat and pressure deep within the Earth's crust, it goes through a process called metamorphism.
2. During metamorphism, the sandstone grains recrystallize and realign under the pressure, forming quartzite, a metamorphic rock that is harder and more resistant than the original sandstone.
3. This transformation from sandstone to quartzite is a result of the metamorphic process, where the mineral composition and texture of the rock change without melting completely.
Therefore, the correct term to complete the statement is "metamorphosed," as it accurately describes the process by which quartzite is formed from sandstone through metamorphism.
