This is a bit of a trick question! The rock cycle encompasses all naturally occurring rocks on Earth. However, there are some materials that might seem like rocks, but are not formed through the processes of the rock cycle:

* Meteorites: These are rocks from space, formed in different processes from those on Earth.

* Tektites: These glassy materials are formed when meteorites impact Earth.

* Man-made materials: Concrete, bricks, asphalt, and other human-made materials are not part of the natural rock cycle.

It's important to remember that even rocks formed from materials outside the Earth, like meteorites, eventually become part of the rock cycle as they erode and are incorporated into the Earth's crust.