A rock that is composed mostly of plagioclase and pyroxene and has formed deep within the Earth is called a gabbro. Gabbro is an intrusive igneous rock, meaning it solidifies from magma that cools slowly beneath the Earth's surface. It is typically found in the lower crust or upper mantle. To determine this answer, one could use their knowledge of rock types and their formation processes or consult geological resources such as textbooks, online databases, or geology experts.
