Rocks are aggregates of minerals.
Igneous rocks crystallize from magma. Sedimentary rocks form by weathering and erosion of preexisting rock to make sediment, which is lithified into rock. Most rocks in Hawaii are igneous. If magma solidifies within the crust, the rock is called an intrusive igneous rock. Intrusive igneous rocks have been exposed by erosion along rift zones of some of the older volcanoes in Hawaii.