Primary mineral

Primary minerals are mineral constituents in rocks and soils that did not subsequently develop during weathering , alteration or soil formation processes ( authigenesis ) near or on the surface of the earth, but were already present after the original formation and consolidation of the rock (or the original rock of the soil) .

The conversion from primary to secondary minerals occurs because the conditions for the formation and stability of these minerals on the earth's surface are no longer given. Physical and chemical weathering processes cause the primary minerals of the parent rock to be crushed and chemically converted into secondary minerals. Alteration processes are processes similar to chemical weathering, but they do not take place on the surface (e.g. due to the action of hydrothermal solutions ).

The most common primary minerals on the earth's surface are the silicates , especially the very resistant quartz (from sandstones , metamorphic , as well as igneous parent rocks). Mica , feldspars , as well as ribbon , chain and sorosilicates represent an intermediate group of weather resistance. Many ore minerals, however, such as B. metallic sulfides weather very easily. Their oxidation products such as goethite or hematite , together with organic matter, cause the brown color of many soils.