Human: What is the best way to determine which type of a rock is igneous, sedimentary, or metamorphic? Assistant: 
The best way to determine whether a rock is igneous, sedimentary, or metamorphic is by looking at its physical characteristics. Metamorphic rocks are usually composed of minerals that have been recrystallized and altered by heat and pressure. Sedimentary rocks are made up of particles that were once part of an ocean or lake bed. Igneous rocks are formed from the cooling of molten magma and can be divided into two categories: intrusive and extrusive. Intrusive rocks form when magma cools within the earth's crust, while extrusive rocks are those that erupt onto the surface.