Correct Option
Quartzite is a metamorphic rock that forms from sandstone. During metamorphism, under conditions of high temperature and pressure, the quartz grains within the sandstone recrystallize and interlock. This process results in a very hard, dense, and non-foliated rock that is highly resistant to weathering.
Incorrect Options
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Limestone: When subjected to metamorphism, limestone, which is primarily composed of calcium carbonate, transforms into marble.
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Obsidian: Obsidian is an extrusive igneous rock, formed from rapidly cooled lava. It is not a parent rock (protolith) for the formation of quartzite through metamorphism.
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Shale: Shale is a sedimentary rock composed of clay minerals. Upon metamorphism, shale typically transforms into foliated metamorphic rocks such as slate, phyllite, schist, and ultimately gneiss, depending on the intensity of metamorphism.