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 5-10% 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 sand-sized 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 fine-grained 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 0.02-0.1mm in size and have characteristic shapes.
– Sparite cement in limestone indicates high-energy 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.https://en.wikipedia.org/wiki/Limestone