Matrix (geology)

The matrix or groundmass of a rock is the finer-grained mass of material in which larger grains, crystals, or clasts are embedded.^[1]

The matrix of an igneous rock is made up of fine-grained, often tiny, crystals in which larger crystals, called phenocrysts, are embedded. In South Africa, diamonds are often mined from a matrix of weathered clay-like rock (kimberlite) called "yellow ground".^[1]

The matrix of sedimentary rocks is made up of finer-grained sedimentary material, such as clay or silt, in which larger grains or clasts are embedded.^[1]

1. ↑ ^{1.0 1.1 1.2} One or more of the preceding sentences incorporates text from a publication now in the public domain: Flett, John Smith (1911). "Petrology". In Chisholm, Hugh (ed.). Encyclopædia Britannica (11th ed.). Cambridge University Press. p. 332.