why is quartzite very hard and more resitant than its parent rock?

earth science lab >.<

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  • 1 decade ago
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    There are really two reasons. One, the grains are more interlocked due to compaction and local dissolution/repercipitation. Two, quatzites are loaded with silica cement, so the whole rock is a 7 hardness and the grains are held together better. The rock's iduvidual hardness does not change, it's more how it is held together.

  • Anonymous
    1 decade ago

    During the process of metamorphysis, rocks descend into the earth until they begin to melt. At these depths, incredible pressure and heat compresses the gooey rock. More specifically, the original quartz sand grains and quartz silica cement that held the sandstone together combine. Over time, this gooey rock comes back up to the surface and cools down. However, the compression due to pressure and heat has transformed the rock into a much harder rock than the sandstone it was made from.

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