Olivine is thought to be an important mineral in Earth’s mantle. Its presence as a mantle mineral has been inferred by a change in the behavior of seismic waves as they cross the Moho – the boundary between Earth’s crust and mantle.

The presence of olivine in Earth’s interior is also confirmed by the presence of olivine in xenoliths, which are thought to be pieces of the upper mantle delivered to Earth’s surface in the magmas of deep-source volcanic eruptions. Olivine is also an abundant mineral in the lower portion of many ophiolites. These are slabs of oceanic crust (with part of the upper mantle attached) that have been thrust up onto an island or a continent.