Answer
As sand undergoes metamorphism and transforms into quartzite, it undergoes a textural change characterized by increased grain size and the recrystallization of quartz grains. The intermediate states are three. Initially, the sand consists of loose grains of various sizes, primarily composed of quartz. The grains are typically rounded and well-sorted. With the application of heat and pressure during the metamorphic process, the loose sand grains become compacted and cemented together to form sandstone. The sand grains are still recognizable, but they are more tightly packed and bonded.
As the metamorphic conditions continue to increase, the sandstone undergoes further recrystallization, and the quartz grains become more tightly interlocked. The original grain boundaries are obliterated, and the sandstone is transformed into quartzite. Quartzite is a hard, durable, and dense rock composed almost entirely of interlocking quartz grains.
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