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Glauconite - glaukonit.jpg
Category Phyllosilicate
(repeating unit)
Crystal system Monoclinic
Crystal class Prismatic (2/m)
(same H-M symbol)
Space group C2/m
Unit cell a = 5.234 Å, b = 9.066 Å,
c = 10.16 Å; β = 100.5°; Z = 2
ColorBlue green, green, yellow green
Crystal habit Elastic platy/micaceous, or as rounded pellets/aggregates
Cleavage Perfect [001]
Mohs scale hardness2
Luster Dull - earthy
Streak Light green
Diaphaneity Translucent to nearly opaque.
Specific gravity 2.4 - 2.95
Optical propertiesBiaxial (-)
Refractive index nα = 1.590 - 1.612 nβ = 1.609 - 1.643 nγ = 1.610 - 1.644
Birefringence δ = 0.020 - 0.032
Pleochroism X = yellow-green, green; Y = Z = deeper yellow, bluish green
Other characteristicsloosely bound aggregates, crumbles
radioactivity: barely detectable
References [1] [2] [3]

Glauconite is an iron potassium phyllosilicate (mica group) mineral of characteristic green color which is very friable [4] and has very low weathering resistance.

Iron Chemical element with atomic number 26

Iron is a chemical element with symbol Fe and atomic number 26. It is a metal, that belongs to the first transition series and group 8 of the periodic table. It is by mass the most common element on Earth, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust.

Potassium Chemical element with atomic number 19

Potassium is a chemical element with symbol K and atomic number 19. It was first isolated from potash, the ashes of plants, from which its name derives. In the periodic table, potassium is one of the alkali metals. All of the alkali metals have a single valence electron in the outer electron shell, which is easily removed to create an ion with a positive charge – a cation, which combines with anions to form salts. Potassium in nature occurs only in ionic salts. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and reacts vigorously with water, generating sufficient heat to ignite hydrogen emitted in the reaction, and burning with a lilac-colored flame. It is found dissolved in sea water, and is part of many minerals.

Silicate minerals Rock-forming minerals with predominantly silicate anions

Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of the Earth's crust.


It crystallizes with a monoclinic geometry. Its name is derived from the Greek glaucos (γλαυκος) meaning 'blue', referring to the common blue-green color of the mineral; its sheen (mica glimmer) and blue-green color presumably relating to the sea's surface. Its color ranges from olive green, black green to bluish green, and yellowish on exposed surfaces due to oxidation. In the Mohs scale it has hardness of 2. The relative specific gravity range is 2.4 - 2.95. It is normally found in dark green rounded brittle pellets, and with the dimension of a sand grain size. It can be confused with chlorite (also of green color) or with a clay mineral. Glauconite has the chemical formula – (K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2.

Greek language language spoken in Greece, Cyprus and Southern Albania

Greek is an independent branch of the Indo-European family of languages, native to Greece, Cyprus and other parts of the Eastern Mediterranean and the Black Sea. It has the longest documented history of any living Indo-European language, spanning more than 3000 years of written records. Its writing system has been the Greek alphabet for the major part of its history; other systems, such as Linear B and the Cypriot syllabary, were used previously. The alphabet arose from the Phoenician script and was in turn the basis of the Latin, Cyrillic, Armenian, Coptic, Gothic, and many other writing systems.

Specific gravity Relative density compared to water

Specific gravity is the ratio of the density of a substance to the density of a reference substance; equivalently, it is the ratio of the mass of a substance to the mass of a reference substance for the same given volume. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance for liquids is nearly always water at its densest ; for gases it is air at room temperature. Nonetheless, the temperature and pressure must be specified for both the sample and the reference. Pressure is nearly always 1 atm (101.325 kPa).

Sand A granular material composed of finely divided rock and mineral particles, from 0.063 to 2 mm diameter

Sand is a granular material composed of finely divided rock and mineral particles. It is defined by size, being finer than gravel and coarser than silt. Sand can also refer to a textural class of soil or soil type; i.e., a soil containing more than 85 percent sand-sized particles by mass.

Glauconite particles are one of the main components of greensand, glauconitic silstone and glauconitic sandstone. Glauconite has been called a marl in an old and broad sense of that word. Thus references to "greensand marl" sometimes refer specifically to glauconite. The Glauconitic Marl formation is named after it, and there is a Glauconitic Sandstone formation in the Mannville Group of Western Canada.


Greensand or green sand is a sand or sandstone which has a greenish color. This term is specifically applied to shallow marine sediment, that contains noticeable quantities of rounded greenish grains. These grains are called glauconies and consist of a mixture of mixed-layer clay minerals, such as smectite and glauconite mica. Greensand is also loosely applied to any glauconitic sediment.

Marl Lime-rich mud or mudstone which contains variable amounts of clays and silt

Marl or marlstone is a calcium carbonate or lime-rich mud or mudstone which contains variable amounts of clays and silt. The dominant carbonate mineral in most marls is calcite, but other carbonate minerals such as aragonite, dolomite, and siderite may be present. Marl was originally an old term loosely applied to a variety of materials, most of which occur as loose, earthy deposits consisting chiefly of an intimate mixture of clay and calcium carbonate, formed under freshwater conditions; specifically an earthy substance containing 35–65% clay and 65–35% carbonate. It also describes a habit of coralline red alga. The term is today often used to describe indurated marine deposits and lacustrine (lake) sediments which more accurately should be named 'marlstone'. Marlstone is an indurated rock of about the same composition as marl, more correctly called an earthy or impure argillaceous limestone. It has a blocky subconchoidal fracture, and is less fissile than shale. The term 'marl' is widely used in English-language geology, while the terms Mergel and Seekreide are used in European references.

In linguistics, a word sense is one of the meanings of a word. Words are in two sets: a large set with multiple meanings and a small set with only one meaning. For example, a dictionary may have over 50 different senses of the word "play", each of these having a different meaning based on the context of the word's usage in a sentence, as follows:

We went to see the playRomeo and Juliet at the theater.

The coach devised a great play that put the visiting team on the defensive.

The children went out to play in the park.

Environment of formation

At the broadest level, glauconite is an authigenic mineral and forms exclusively in marine settings. [5] It is commonly associated with low-oxygen conditions. [6]

Normally, glauconite is considered a diagnostic mineral indicative of continental shelf marine depositional environments with slow rates of accumulation. For instance, it appears in Jurassic/lower Cretaceous deposits of greensand, so-called after the coloration caused by glauconite. It can also be found in sand or clay formations, or in impure limestones and in chalk. It develops as a consequence of diagenetic alteration of sedimentary deposits, bio-chemical reduction and subsequent mineralogical changes affecting iron-bearing micas such as biotite, and is also influenced by the decaying process of organic matter degraded by bacteria in marine animal shells. Glauconite forms under reducing conditions in sediments and such deposits are commonly found in nearshore sands, open oceans and the Mediterranean Sea. Glauconite remains absent in fresh-water lakes, but is noted in shelf sediments of the western Black Sea. [7] The wide distribution of these sandy deposits was first made known by naturalists on board the fifth HMS Challenger, in the expedition of 1872–1876.

Continental shelf A portion of a continent that is submerged under an area of relatively shallow water known as a shelf sea

A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water known as a shelf sea. Much of the shelves were exposed during glacial periods and interglacial periods.

The Jurassic was a geologic period and system that spanned 56 million years from the end of the Triassic Period 201.3 million years ago (Mya) to the beginning of the Cretaceous Period 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles. The start of the period was marked by the major Triassic–Jurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian-Toarcian extinction in the Early Jurassic, and the Tithonian event at the end; however, neither event ranks among the "Big Five" mass extinctions.

The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago (mya) to the beginning of the Paleogene Period 66 mya. It is the last period of the Mesozoic Era, and the longest period of the Phanerozoic Eon. The Cretaceous Period is usually abbreviated K, for its German translation Kreide.


Glauconite has long been used in Europe as a green pigment for artistic oil paint under the name green earth. [8] [9] One example is its use in Russian "icon paintings", another widespread use was for underpainting of human flesh in medieval painting. [10] It is also found as mineral pigment in wall paintings from the ancient Roman Gaul. [11] Glauconite, a major component of greensand, is also a common source of potassium in plant fertilizers and is also used to adjust soil pH. It is used for soil conditioning in both organic and nonorganic farming, whether as an unprocessed material (for mixing in at proper proportions) or as a feedstock in the synthesis of commercial fertilizer powders.

Pigment material that changes the color of reflected or transmitted light

A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light. Most materials selectively absorb certain wavelengths of light. Materials that humans have chosen and developed for use as pigments usually have special properties that make them useful for coloring other materials. A pigment must have a high tinting strength relative to the materials it colors. It must be stable in solid form at ambient temperatures.

Green earth, also known as terre verte and Verona green, is an inorganic pigment derived from the minerals celadonite and glauconite. Its chemical formula is K[(Al,FeIII),(FeII,Mg](AlSi3,Si4)O10(OH)2.

Icon religious work of art, generally a panel painting, in Eastern Christianity

An icon is a religious work of art, most commonly a painting, in the cultures of the Eastern Orthodox Church, Oriental Orthodoxy, the Roman Catholic, and certain Eastern Catholic churches. The most common subjects include Christ, Mary, saints and angels. Though especially associated with "portrait" style images concentrating on one or two main figures, the term also covers most religious images in a variety of artistic media produced by Eastern Christianity, including narrative scenes.

In Brazil, greensand refers to a fertilizer produced from glauconitic siltstone, unit belonging to the Serra da Saudade Formation, Bambuí Group, of Neoproterozoic/Ediacaran age. The outcrops occur [12] in the Serra da Saudade ridge, in the Alto Paranaíba region, Minas Gerais state. It is a silty-clayed sedimentary rock, laminated, bluish-green, composed of glauconite (40-80%), potassium feldspar (10-15%), quartz (10-60%), muscovite (5%) and minor quantities of biotite (2%), goethite (<1%), titanium and manganese oxides (<1%), barium phosphate and rare-earth element phosphates (<1%).

Enriched levels of potash have K2O grades between 8 and 12%, thickness up to 50 m and are associated to the glauconitic levels, dark-green in color. Glauconite is authigenic and highly mature. The high concentration of this mineral is related to a depositional environment with a low sedimentation rate. The glauconitic siltstone has resulted from a high level flooding event in the Bambuí Basin. The sedimentary provenance is from supracrustal felsic elements on continental margin environment with acid magmatic arc (foreland basin).

Related Research Articles

Shale A fine-grained, clastic sedimentary rock

Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. Shale is characterized by breaks along thin laminae or parallel layering or bedding less than one centimeter in thickness, called fissility. It is the most common sedimentary rock.

Sedimentary rock Rock formed by the deposition and subsequent cementation of material

Sedimentary rocks are types of rock that are formed by the deposition and subsequent cementation of mineral or organic particles on the floor of oceans or other bodies of water at the Earth's surface. Sedimentation is the collective name for processes that cause these particles to settle in place. The particles that form a sedimentary rock are called sediment, and may be composed of geological detritus (minerals) or biological detritus. Before being deposited, the geological detritus was formed by weathering and erosion from the source area, and then transported to the place of deposition by water, wind, ice, mass movement or glaciers, which are called agents of denudation. Biological detritus was formed by bodies and parts of dead aquatic organisms, as well as their fecal mass, suspended in water and slowly piling up on the floor of water bodies. Sedimentation may also occur as dissolved minerals precipitate from water solution.


The Gault Formation is a geological formation of stiff blue clay deposited in a calm, fairly deep-water marine environment during the Lower Cretaceous Period. It is well exposed in the coastal cliffs at Copt Point in Folkestone, Kent, England, where it overlays the Lower Greensand formation, and underlies the Upper Greensand Formation. These represent different facies, with the sandier parts probably being deposited close to the shore and the clay in quieter water further from the source of sediment; both are believed to be shallow-water deposits.

Celadonite mica, phyllosilicate mineral

Celadonite is a mica group mineral, a phyllosilicate of potassium, iron in both oxidation states, aluminium and hydroxide with formula: K(Mg,Fe2+)(Fe3+,Al)[Si4O10](OH)2.

The Perth Basin is a thick, elongated sedimentary basin in Western Australia. It lies beneath the Swan Coastal Plain west of the Darling Scarp, representing the western limit of the much older Yilgarn Craton, and extends further west offshore. Cities and towns including Perth, Busselton, Bunbury, Mandurah and Geraldton are built over the Perth Basin.

Clastic rock type of sedimentary rock

Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus, chunks and smaller grains of rock broken off other rocks by physical weathering. Geologists use the term clastic with reference to sedimentary rocks as well as to particles in sediment transport whether in suspension or as bed load, and in sediment deposits.

Chugwater Formation

The Chugwater Formation is a mapped bedrock unit consisting primarily of red sandstone, in the states of Wyoming, Montana, and Colorado in the United States. It is recognized as a geologic formation in Colorado and Montana, but as a Group in Wyoming.

Authigenesis mineral or sedimentary rock deposit is that was generated where it is found or observed

Authigenesis is the process whereby a mineral or sedimentary rock deposit is generated where it is found or observed. Such deposits are described as authigenic. Authigenic sedimentary minerals form during sedimentation by precipitation or recrystallization instead of being transported from elsewhere (allogenic) by water or wind. Authigenic sediments are the main constituents of deep sea sedimentation. Authigenic clays tend to reduce the porosity of sediments, thus reducing permeability.

This glossary of geology is a list of definitions of terms and concepts relevant to geology, its sub-disciplines, and related fields. For other terms related to the Earth sciences, see Glossary of geography terms.

The Lower Greensand Group is a geological unit, which forms part of the underlying geological structure of southeast England. South of London in the counties of West Sussex, East Sussex, Surrey and Kent, which together form the wider Weald, the Lower Greensand can usually be subdivided to formational levels with varying properties into the Atherfield Clay Formation, the Hythe Formation, the Sandgate Formation, and the Folkestone Formation. In areas north and west of London, including Cambridgeshire, Bedfordshire and Buckinghamshire the Lower Greensand is referred to as the Woburn Sands Formation.

Geology of East Sussex

The geology of East Sussex is defined by the Weald–Artois anticline, a 60 kilometres (37 mi) wide and 100 kilometres (62 mi) long fold within which caused the arching up of the chalk into a broad dome within the middle Miocene, which has subsequently been eroded to reveal a lower Cretaceous to Upper Jurassic stratigraphy. East Sussex is best known geologically for the identification of the first dinosaur by Gideon Mantell, near Cuckfield, to the famous hoax of the Piltdown man near Uckfield.

The geology of West Sussex in southeast England comprises a succession of sedimentary rocks of Cretaceous age overlain in the south by sediments of Palaeogene age. The sequence of strata from both periods consists of a variety of sandstones, mudstones, siltstones and limestones. These sediments were deposited within the Hampshire and Weald basins. Erosion subsequent to large scale but gentle folding associated with the Alpine Orogeny has resulted in the present outcrop pattern across the county, dominated by the north facing chalk scarp of the South Downs. The bedrock is overlain by a suite of Quaternary deposits of varied origin. Parts of both the bedrock and these superficial deposits have been worked for a variety of minerals for use in construction, industry and agriculture.

Rencontre Formation

The Rencontre Formation is a geological formation just below the Cambrian-Ediacaran boundary in Newfoundland, deposited in a fault-bounded enclosed basin. U-Pb dates obtained just below its base give a maximum age of 552 ± 3 million years ago

The geology of Georgia is the study of rocks, minerals, water, landforms and geologic history in Georgia. The country is dominated by the Caucasus Mountains at the junction of the Eurasian Plate and the Afro-Arabian Plate, and rock units from the Mesozoic and Cenozoic are particularly prevalent. For much of its geologic history, until the uplift of the Caucasus, Georgia was submerged by marine transgression events. Geologic research for 150 years by Georgian and Russian geologists has shed significant light on the region and since the 1970s has been augmented with the understanding of plate tectonics.

Geology of Bosnia and Herzegovina

The geology of Bosnia & Herzegovina is the study of rocks, minerals, water, landforms and geologic history in the country. The oldest rocks exposed at or near the surface date to the Paleozoic and the Precambrian geologic history of the region remains poorly understood. Complex assemblages of flysch, ophiolite, mélange and igneous plutons together with thick sedimentary units are a defining characteristic of the Dinaric Alps, also known as the Dinaride Mountains, which dominate much of the country's landscape.

Geology of North Macedonia

The geology of North Macedonia includes the study of rocks dating to the Precambrian and a wide-array of volcanic, sedimentary and metamorphic rocks formed in the last 541 million years.

The geology of Lithuania consists of ancient Proterozoic basement rock overlain by thick sequences of Paleozoic, Mesozoic and Cenozoic marine sedimentary rocks, with some oil reserves, abundant limestone, dolomite, phosphorite and glauconite. Lithuania is a country in the Baltic region of northern-eastern Europe.


  1. Handbook of Mineralogy
  2. Webmineral
  3. Mindat
  4. Odin, G.S. (ed., 1988). Green marine clays. Development in sedimentology, 45. Elsevier, Amsterdam.
  5. Smith, S. A., and R. N. Hiscott. 1987: Latest precambrian to Early Cambrian basin evolution, Fortune Bay, Newfoundland fault–bounded basin to platform. Canadian Journal of Earth Sciences 21:1379–1392.
  6. Hiscott, R. N. 1982: Tidal deposits of the Lower Cambrian Random Formation, eastern Newfoundland; facies and paleoenvironments. Canadian Journal of Earth Sciences 19:2028–2042.
  7. H, Suttill (2009) SEDIMENTOLOGICAL EVOLUTION OF THE EMINE & KAMCHIA BASINS, EASTERN BULGARIA. Thesis submitted for the degree of Master of Philosophy. Available from: the University of Edinburgh
  8. Grissom, C.A. Green Earth, in Artists’ Pigments. A Handbook of Their History and Characteristics, Vol. 1, L. Feller, (Ed), Cambridge University Press, London 1986, pp. 141 – 167
  9. Green earth Colourlex
  10. Grissom, C.A. Green Earth, in Artists’ Pigments. A Handbook of Their History and Characteristics, Vol. 1, L. Feller, (Ed), Cambridge University Press, London 1986, p. 143
  11. Eastaugh, N "Pigment Compendium: A Dictionary of Historical Pigments", page 169. Elsevier, 2004