The geologist has identified an igneous rock, specifically a type known as granite or similar, as indicated by its coarse-grained texture with large round grains. This texture typically forms when lava cools slowly beneath the Earth's surface, allowing larger crystals to grow. However, if the context is that the lava cooled on the Earth's surface, the rock could also be a form of volcanic rock, such as rhyolite if it is fine-grained. If it has larger grains but cooled quickly, it could also be a form of porphyritic rock.
Nonetheless, given the details provided—massive rock outcrop, coarse-grained texture, and cooling on the surface—the most likely identification is a volcanic igneous rock, potentially rhyolite or a porphyritic variant if there are the larger grains within a finer matrix. Generally speaking, more specific identification might require additional context about the rock's mineral composition and other characteristics.
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