Peridotite is one of the main materials of the upper mantle, and both basaltic and gabbroic magma are thought to be produced by the melting of peridotite in the mantle. So ultimately, mantle peridotite is the source of most of the material that makes up the rocks of the Earth's crust. Laboratory tests have shown that if peridotite is heated to melting point, the melt is basalt. Partial melting seems to give picrites and komatiites.