Earth's core has two parts, a solid iron inner core and a molten outer core, which is composed of a nickel-iron alloy. The outer core begins about 1,800 miles under the crust.
It is believed that the core also contains a large amount of gold and platinum, so much that if it was poured onto the surface it would cover the entire planet up to 1 1/2 feet. The inner core is solid and has a radius of about 760 miles. The outer core is about 1,400 miles thick and is mostly molten liquid. The entire core is about the size of the planet Mars.