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Some rocks have sparkly bits inside called crystals.

Some rocks have sparkly bits inside called crystals.

Crystals grow in shiny shapes with flat, smooth sides. When light hits them, they can twinkle and glitter.

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Sand is made of tiny bits of rock and shell. Sand is made of tiny bits of rock and shell. Rivers can turn rough rocks into smooth, round pebbles. Rivers can turn rough rocks into smooth, round pebbles. Volcanoes make brand-new rock when their lava cools. Volcanoes make brand-new rock when their lava cools. Sand can be many colours, even white, pink, or black. Sand can be many colours, even white, pink, or black. Diamond is the hardest natural material on Earth. Diamond is the hardest natural material on Earth.