Limestone

Composition and Characteristics of Limestone: Limestone is primarily composed of calcite and aragonite, forms of calcium carbonate. Dolomite is rare in limestone. Limestone is chemically pure with less than 510% clastic sediments. Silica, in the form of chert or siliceous skeletal fragments, is common in limestone. Limestone varies in color, density, and hardness. Grains in Limestone: Grains in limestone are mainly skeletal fragments of marine organisms like coral and foraminifera. Other carbonate grains include ooids, peloids, and limeclasts. Ooids are sandsized grains with calcite or aragonite layers. Peloids are structureless grains likely produced by various processes. Formation and Uses of Limestone: Limestone forms from the precipitation of minerals like calcite and aragonite from water containing dissolved calcium. Most limestone is formed in shallow marine environments. Limestone is utilized in cement production, as aggregate for roads, white pigment, soil conditioner, and decorative rock gardens. Limestone formations are associated with petroleum reservoirs and cave systems. Micrite and Sparry Calcite in Limestone: Carbonate mud in limestone contains micrite, which is finegrained carbonate mud with microlites. Micrite can precipitate from seawater, be secreted by algae, or result from abrasion of carbonate grains. Sparry calcite crystals in limestone are typically 0.020.1mm in size and have characteristic shapes. Sparite cement in limestone indicates highenergy depositional environments. Identifying Limestone and Related Characteristics: Limestone outcrops are recognized by their softness and reaction with hydrochloric acid. Dolomite shares softness characteristics with limestone. Sparite in limestone has a grain size over 20μm and appears white or transparent. The White Cliffs of Dover are composed of chalk, a type of limestone with distinctive features.