The two rock characteristics that are used to determine the processes that created a rock are texture and mineral composition.
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A rock's texture, which includes the shape, size, and arrangement of crystals gives an appearance of a rock. The mineral composition reflects the geological process that was used to create the rock. For example, granite has large crystals that are light colored, which result from the slow cooling of molten rock deep beneath the surface. On the other hand, there is basalt that is rich in dark minerals and occurs from rapid cooling of molten rock on Earth's surface. This gives basalt microscopically small crystals and a smooth texture.