A sample of glauconite

Glauconite is a phyllosilicate (mica group) mineral of formula: (K,Na)(Fe³⁺,Al,Mg)₂(Si,Al)₄O₁₀(OH)₂. It can also be referred to as an iron silicate. It crystallizes with monoclinic geometry. The name is derived from the Greek glaucos (γλαυκος) meaning 'gleaming' or 'silvery', to describe the appearance of the blue-green color, presumably relating to the sheen and blue-green colour of the sea's surface. Its color ranges from olive green, black green to bluish green. It is probably the result of the iron content of the mineral. In the Mohs scale it has hardness of 2. The relative density range is 2.2 - 2.8. It is normally found in dark green rounded nodules of sand size dimension. It can be confused with chlorite or with some clays. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... The silicate minerals make up the largest and most important class of rock-forming minerals. ... For other uses, see Mica (disambiguation). ... Minerals are natural compounds formed through geological processes. ... General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Atomic mass 39. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ... General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white Atomic mass 24. ... It has been suggested that Silicons ranking be merged into this article or section. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... This article is about the chemistry of hydrogen. ... Crystal (disambiguation) Insulin crystals A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... In crystallography, the monoclinic crystal system is one of the 7 lattice point groups. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer. ... In physics, density is defined as mass m per unit volume V. For the common case of a homogeneous substance, it is expressed as: where, in SI units: ρ (rho) is the density of the substance, measured in kg·m-3 m is the mass of the substance, measured in kg... Patterns in the sand Sand is a granular material made up of fine rock particles. ... Chlorite is a group of phyllosilicate minerals often classified as clays. ... The Gay Head cliffs in Marthas Vineyard are made almost entirely of clay. ...

Normally, glauconite is considered diagnostic of continental shelf marine depositional environments with slow rates of accumulation. Typically, it appears in Jurassic/lower Cretaceous deposits of Greensand, so-called after the colouration provided by the glauconite. It can also be found in impure limestones, such as Kentish Rag and in Chalk. It develops as a consequence of diagenetic alteration of sedimentary deposits, changes in the biotite micas, for example, being influenced by the decaying process of the organic matter in animal shells. Glauconite forms under reducing conditions in sediments and such deposits are commonly found in nearshore sandstones, open oceans and the Mediterranean Sea but not in the Black Sea or in fresh-water lakes. It oxidises on contact with air; the resulting deoxygenated air is a hazard to miners.  Sediment  Rock  Mantle  The global continental shelf, highlighted in cyan The continental shelf is the extended perimeter of each continent, which is covered during interglacial periods such as the current epoch by relatively shallow seas (known as shelf seas) and gulfs. ... // The image above is believed to be a replaceable fair use image. ... The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i. ... Greensand is an olive-green coloured sandstone rock which found in narrow bands, particularly associated with bands of chalk and clay in northern and western Europe. ... The Needles,situated on the Isle Of Wight, are part of the extensive Southern England Chalk Formation. ... In geology and oceanography, diagenesis is any chemical, physical, or biological change undergone by a sediment after its initial deposition and during and after its lithification, exclusive of surface alteration (weathering) and metamorphism. ... A Biotite slice Biotite is a common phyllosilicate mineral that contains potassium, magnesium, iron and aluminium. ... Red sandstone interior of Lower Antelope Canyon, Arizona, worn smooth due to erosion by flash flooding over millions of years Sandstone is a sedimentary rock composed mainly of sand-size mineral or rock grains. ... Composite satellite image of the Mediterranean Sea. ... NASA satellite image of the Black Sea Map of the Black Sea The Black Sea is an inland sea between southeastern Europe and Anatolia that is actually a distant arm of the Atlantic Ocean by way of the Mediterranean Sea. ...

Glauconite has long been used in Europe as an artistic oil paint, especially in Russian "icon paintings". It is rated as a highly permanent pigment, and often marketed by the names "terre verte" or "green earth". [1] Look up icon in Wiktionary, the free dictionary. ... For animal and plant pigments, see Pigment, biology. ...

The wide distribution of these sandy deposits was first made known by naturalists on board H.M.S. Challenger (expedition of 1872-1876. Year 1872 (MDCCCLXXII) was a leap year starting on Monday (link will display the full calendar) of the Gregorian Calendar (or a leap year starting on Wednesday of the 12-day slower Julian calendar). ... 1876 (MDCCCLXXVI) was a leap year starting on Saturday. ...

See also

• List of minerals
• Greensand