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A geologist is studying a massive rock outcrop. The texture of the rock is coarse-grained with large round grains. The geologist determines that the rock probably formed when lava cooled on Earth’s surface.

What type of rock has the geologist identified?

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Answered by GPT-5 mini AI
An igneous rock — specifically an extrusive (volcanic) rock. The large rounded crystals are phenocrysts, giving a porphyritic texture produced when magma began crystallizing slowly (forming large grains) and then erupted and finished cooling quickly at the surface.