undersaturated rock

In geology, "undersaturated rock" refers to igneous rocks that contain minerals which are deficient in silica. This means that the magma from which these rocks formed did not have enough silica to combine with all the available metallic oxides to create specific silicate minerals. Instead, minerals like magnesium-olivine, nepheline, and leucite form, which require less silica than other common silicate minerals. These rocks are typically enriched in iron and magnesium and depleted in silica compared to "saturated" or "supersaturated" rocks, which may contain quartz or minerals that require more silica. The term "undersaturation" itself simply describes the state of not being fully saturated.12