Crystals are solid substances that have their atoms arranged in regular patterns. Most naturally occurring substances form crystals under the right conditions, although they are not always apparent. Crystals form into regular geometric shapes, and crystals of the same substance or mixture of substances will always have the same regular appearance.
Crystals are formed from solutions or melted materials. As the solutions evaporate or the melted materials cool, their atoms are forced closer together, producing a crystal. This crystal gradually grows as the process continues. Some crystals grow into complicated and beautiful shapes, which are often brightly coloured.
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