Chemical weathering changes the composition of the rock material toward surface minerals, such as clays. It attacks minerals that are relatively unstable in surface conditions, such as the primary minerals of igneous rocks like basalt, granite or peridotite.
Water is especially effective at introducing chemically active agents by way of fractures and causing rocks to crumble piecemeal or by loosening thin shells of material (in spheroidal weathering). Chemical weathering may include shallow, low-temperature alteration.
See examples of these in the chemical weathering picture gallery.
Chemical weathering is an element of corrosion or chemical erosion.