The forces of weather on the surface of the Earth can change the minerals that make up rocks. When mechanical weathering processes destroy old rocks, softer silicate minerals such as olivine and plagioclase may dissolve away, leaving behind harder minerals, such as quartz. In chemical weathering, the atoms react with oxygen or water in the environment. (Think of iron exposed for several months to the water and air outdoors. The iron rusts, and rusting is a kind of chemical weathering.) In the presence of water, some minerals transform into more hydrous minerals. Other minerals, such as calcite (calcium carbonate), dissolve completely in water over time. Some silicate minerals, such as quartz and garnet, are more resistant to weathering than other silicates, such as feldspar and mica.

Pseudomorphs are minerals that have been chemically altered, so that they are new minerals that retain the shape of the original mineral. (The word "pseudomorphic" means "false form" in Greek.) Changes in a mineral's environment can cause the replacement of one mineral with another, atom by atom. In one example, limonite, a type of iron oxide hydroxide, substitutes itself in for pyrite, or iron sulfide, but the crystals are still shaped like the original pyrite. Geologists call the resulting mineral "limonite after pyrite." Another example of pseudomorphism occurs when quartz replaces crocidolite, a variety of riebeckite that is a source of asbestos fibers. The resulting solid mineral retains a fibrous internal structure that gives the stone a particular sheen known as chatoyancy, or the "cat's eye" effect.

When some minerals are ground into powders, they may be used as pigments, solid substances that change the color of the materials they are mixed with. The first pigments, known since prehistoric times, were iron oxides, which make warm, dark reds and browns. Other early pigments were made of lead, carbon (in charcoal form), malachite, and azurite. Today's paints may contain synthetic dyes in addition to natural pigments and fillers such as calcium carbonate, mica, silica, talc, and titanium dioxide. Minerals have been used as ingredients in facial makeup at least since the days of ancient Egypt, when women painted their eyes with kohl, a mixture containing finely ground galena, or lead sulfide. Modern-day cosmetics manufacturers avoid hazardous substances like lead and arsenic, but many of their products contain microscopic particles of minerals and their derivatives such as iron oxide (from goethite and other minerals), titanium dioxide (usually from ilmenite), talc, mica, and kaolinite.