Peridotite, quartz, and nickel are some of the most common compounds that make up Earth. Peridotite has a density of approximately 3.4 g/cm3; quartz has a density of approximately 2.65 g/cm3; and nickel has a density of approximately 8.9 g/cm3. Based on this information, which compound do you think is most common near Earth’s surface, and which do you think is most common near Earth’s core?