Micritic limestone

Micritic limestone is a type of rock classified in geology as limestone. Limestone is a sedimentary rock consisting mainly of the chemical compound calcium carbonate (CaCO3) in the form of the minerals calcite and aragonite[1External link]. Micrite refers to the part of limestone that consists of the smaller grain sizes and often forms the matrix of a limestone[3External link].

Micritic limestone is referred to as a solid, consolidated calcareous mud consisting of carbonate grains with a grain size of less than 63 µm. The crystal faces of micrite grains are either indistinct or invisible to the naked eye. As a result, micrite does not shine or sparkle in hand specimens. According to Folk's (1962) classification, limestones are called micritic when the bulk of the rock is composed mainly of micrite matrix (instead of the often coarser sparite cement). The rock designation of a micritic limestone depends on the nature of the coarser carbonate components surrounded by the micrite matrix: If they consist predominantly of intraskeletal fragments, they are called intramicrites. Oomicrites, pelmicrites and onkomicrites contain ooids, peloids and oncoids, respectively, in addition to micrite. Biomicrites are dominated by biogenic constituents such as shell fragments[3External link].

Limestones, including micritic limestones, have a wide economic importance as building materials in the construction industry and as natural stone. They also serve as reservoir rocks for petroleum and natural gas. Limestones can be biogenic, chemically precipitated, or clastic in origin. The composition of limestone is primarily calcite and aragonite, with varying proportions of other minerals such as clay minerals, dolomite, quartz, or  gypsum[1External link][4External link]. Micritic limestones have a fine, microcrystalline structure and can be named differently depending on the nature of the included components, e.g. intramicrite, oomicrite, pelmicrite or biomicrite[3External link].

The color of limestone usually varies from white to ocher, depending on the presence of manganese, iron oxides, and other colored minerals. Limestone has a relatively low hardness of 3 on the Mohs scale and a density of 2.6 to 2.9 kg/dm3 for dense (non-porous) limestone[1External link].