Rocks are the primary source of all plant nutrients, except nitrogen. These nutrients are bound into a variety of crystalline structures (minerals). Minerals are either formed during rock formation from magma (primary mineral) or formed during soil formation (secondary minerals). Secondary minerals are formed when the local soil solution is saturated in respect to that mineral. In contrast to secondary minerals, for primary minerals the soil solution is generally undersaturated, causing these minerals to dissolve. But  this text dissolution process is extremely slow for most minerals. It has been estimated that it takes more than 30 million years to dissolve a 1 mm diameter quartz grain under natural soil conditionsLasaga 1984. Nonetheless, soil mineral weathering provides an essential input of plant nutrients into ecosystems, avoiding or delaying nutrient limitationsChadwick 1999.