what is a gem made up of
Gems form in many different environments in the Earth. We will examine the most common and important environments and formation processes in this lecture. It is important to distinguish where gems are formed from where they are found. Almost all gems are formed below the Earth's surface. 1  Some are brought to the surface through mining. 2  Some are brought to the surface through earth processes (faulting, folding, large scale uplift, volcanism). These processes can move rock up from more than 400 km below the surface.