Here's why:
* Sandstone composition: Sandstone is primarily composed of quartz grains, which are very resistant to chemical alteration.
* Heat and pressure: The heat from the nearby magma and the pressure from the overlying rocks cause the quartz grains in the sandstone to recrystallize and interlock.
* Recrystallization: This recrystallization process results in a tightly packed, hard, and dense rock with a sugary or glassy texture, which is characteristic of quartzite.
Other metamorphic rocks can also form from sandstone, depending on the specific conditions:
* Hornfels: This rock forms when sandstone is subjected to intense heat from a nearby magma body.
* Slate: If the sandstone contains clay minerals, it can transform into slate, a fine-grained metamorphic rock with a characteristic cleavage.
However, quartzite is the most common metamorphic rock formed from sandstone near Earth's surface due to the abundance of quartz in sandstone and the typical conditions associated with magma intrusion.
