The outer core of the Earth is not composed of rocks in the traditional sense. It's a liquid layer, primarily made up of iron (Fe) and nickel (Ni), with smaller amounts of other elements like sulfur, silicon, and oxygen.

Here's why we can't call it "rock":

* State of Matter: Rocks are solid. The outer core is a liquid due to intense heat and pressure.

* Composition: While rocks are made of minerals, the outer core is mostly composed of metals.

So, while we don't talk about "types of rocks" in the outer core, we do refer to its composition and properties.