Glauconite

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

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.

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.

Glauconite
Mineraly.sk - glaukonit
General
CategoryPhyllosilicate
Formula
(repeating unit)
(K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/m
Unit cella = 5.234 Å, b = 9.066 Å,
c = 10.16 Å; β = 100.5°; Z = 2
Identification
ColorBlue green, green, yellow green
Crystal habitElastic platy/micaceous, or as rounded pellets/aggregates
CleavagePerfect [001]
Mohs scale hardness2
LusterDull - earthy
StreakLight green
DiaphaneityTranslucent to nearly opaque.
Specific gravity2.4 - 2.95
Optical propertiesBiaxial (-)
Refractive indexnα = 1.590 - 1.612 nβ = 1.609 - 1.643 nγ = 1.610 - 1.644
Birefringenceδ = 0.020 - 0.032
PleochroismX = yellow-green, green; Y = Z = deeper yellow, bluish green
Other characteristicsloosely bound aggregates, crumbles
radioactivity: barely detectable
References[1][2][3]

Occurrence

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.

Uses

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]

Fertilizers

Glauconite, a major component of greensand, is also a common source of potassium (K) 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. 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).

References

  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
  12. ^ Silvano MOREIRA, Débora (2016). "ESTRATIGRAFIA, PETROGRAFIA E MINERALIZAÇÃO DE POTÁSSIO EM SILTITOS VERDES DO GRUPO BAMBUÍ NA REGIÃO DE SÃO GOTARDO, MINAS GERAIS" (PDF). Revista Geociências. 35: 157–171 – via UNESP.
Aluminoceladonite

Aluminoceladonite is a low-temperature potassium dioctahedral mica mineral which is an end-member in the illite-aluminoceladonite solid solution series. The chemical formula for aluminoceladonite is K(Mg,Fe2+)Al(Si4O10)(OH)2.

Castle Hayne Limestone

The Castle Hayne Limestone (also called the Castle Hayne Formation) is a geologic formation in North Carolina. It consists of cobble to pebble sized clasts, usually rounded, coated with phosphate and glauconite in a limestone matrix. The Castle Hayne Limestone is known for containing fossils dating back to the Paleogene period. It preserves many of North Carolina's renowned Eocene fossils. It is named after the locality of Castle Hayne in New Hanover county, though the formation itself stretches over several counties.

Celadonite

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.

It crystallizes in the monoclinic system and usually forms massive aggregates of prismatic crystallites or in dull clay masses. It is soft with a Mohs hardness of 2 and a specific gravity of 3. Typically occurs as dull gray-green to bluish green masses. It forms vesicle fillings and linings in altered basaltic lavas.

It was first described in 1847 on Monte Baldo, near Verona, Italy. The name is from the French celadon, for sea-green. It is one of two minerals, along with glauconite, used in making the pigment known as green earth.

Crag Group

The Crag Group is a geological group outcropping in East Anglia, UK and adjacent areas of the North Sea. Its age ranges from approximately 4.4 to 0.478 million years BP, spanning the late Pliocene and early to middle Pleistocene epochs. It comprises a range of marine and estuarine sands, gravels, silts and clays deposited in a relatively shallow-water, tidally-dominated marine embayment on the western margins of the North Sea basin. The sands are characteristically dark green from glauconite but weather bright orange, with haematite 'iron pans' forming. The lithology of the lower part of the Group is almost entirely flint. The highest formation in the Group, the Wroxham Crag, contains over 10% of far-travelled lithologies, notably quartzite and vein quartz from the Midlands, igneous rocks from Wales, and chert from the Upper Greensand of southeastern England. This exotic rock component was introduced by rivers such as the Bytham River and Proto-Thames.

The constituent formations of the Crag Group are the Coralline Crag (mid to late Pliocene); the Red Crag (late Pliocene / early Pleistocene); the Norwich Crag (early Pleistocene) and the Wroxham Crag (early to Middle Pleistocene). The sedimentary record is incomplete, leading to difficulties in correlating and dating sequencesThe term Crag was first used in a geological sense by R.C. Taylor in 1823, a word commonly used in Suffolk to designate any shelly sand or gravel .

Eridania Lake

Eridania Lake is a theorized ancient lake on Mars with a surface area of roughly 1.1 million square kilometers. It is located at the source of the Ma'adim Vallis outflow channel and extends into Eridania quadrangle and the Phaethontis quadrangle. As Eridania Lake dried out in the late Noachian epoch it divided into a series of smaller lakes.

Later research with CRISM found thick deposits, greater than 400 meters thick, that contained the minerals saponite, talc-saponite, Fe-rich mica (for example, glauconite-nontronite), Fe- and Mg-serpentine, Mg-Fe-Ca-carbonate and probable Fe-sulphide. The Fe-sulphide probably formed in deep water from water heated by volcanoes. Such a process, classified as hydrothermal may have been a place where life began.

Flysch

Flysch () is a sequence of sedimentary rock layers that progress from deep-water and turbidity flow deposits to shallow-water shales and sandstones. It is deposited when a deep basin forms rapidly on the continental side of a mountain building episode. Examples are found near the North American Cordillera, the Alps, the Pyrenees and the Carpathians.

Geography of Kent

Kent is the south-easternmost county in England. It is bounded on the north by the River Thames and the North Sea, and on the south by the Straits of Dover and the English Channel. The continent of Europe is 21 miles across the

straits.The major geographical features of the county are determined by a series of ridges running from west to east across the county. These ridges are the remains of the Wealden dome, a denuded anticline across Kent, Surrey and Sussex, which was the result of uplifting caused by the Alpine movements between 10-20 million years ago. The dome was formed of an upper layer of Chalk above subsequent layers of Upper Greensand, Gault, Lower Greensand, Weald Clay and the Hastings Beds. The top of the dome eventually eroded away through weathering and ridges and valleys resulted across Kent and Sussex due to the exposed clay eroding at a faster rate than the exposed chalk, greensand and red sandstone and normal sandstone. The following ridges and the valleys have formed across Kent, listed from north to south:

the low lying London Clay marshlands along the Thames/Medway estuaries and along the North Kent coast;

the chalk North Downs, containing the highest point of the county, Betsom's Hill, at 251m/823 ft.

the Vale of Holmesdale formed from Gault Clay overlaid in the north with the upper layer greensand;

the Greensand Ridge, formed from the lower layer of greensand, containing the source of the River Medway and its tributaries;

the Low Weald, a Weald Clay valley

the sandstone High Weald.The chalk comes in three layers: the upper layer, about 500 feet thick, is a pure white limestone bedded and jointed with localised masses of flint (ideal for cement); the middle layer, about 170 feet thick, is a compact white chalk occasionally hard enough for building; the lower layer, about 170 feet thick, is a greyish marly chalk.Dartford, Gravesend, The Medway Towns, Sittingbourne, Faversham, Canterbury, Deal and Dover are built on chalk.The eastern part of the Wealden dome was eroded away by the sea. The White cliffs of Dover occur where the North Downs meets the coast. From there to Westerham is now the Kent Downs Area of Outstanding Natural Beauty. The chalk displays all its characteristic features such as steep sided dry valleys, and sunken roads.

Greensand is a calcareous sandstone containing an uneven distribution of the mineral glauconite, giving the sandstone a greenish tinge. On exposure to the air this oxidises into a yellow stain. Sevenoaks, Maidstone, Ashford, and Folkestone are built on the greensand. Greensand comes in four layers: the Folkestone Beds 60–250 ft thick; The Sandgate Beds 5–120 ft thick; the Hythe beds 60–350 ft thick and Atherfield Clays 15–50 ft thick. The soil of the greensand is quite varied, ranging from fertile to fairly sterile. On the fertile soils we see chestnut and stands of hazel and oak, while Scots Pine and Birch colonise the poorer soils.The Hastings Beds, which are resistant to weathering, leading to outcrops, such as High Rocks Tunbridge Wells, and sterile soil only suited to heathland and forests of Scots Pine. The Hastings Beds are divided into three formations: Tunbridge Wells Sand Formation 130–400 ft; Wadhurst Clay Formation 100–230 ft, shales with bands of sandstone and iron ore; and the Ashdown Formation 160–700 ft; sandstones. The Fairlight Clays form the upper part of the Ashdown Formation; grey and varigated shales. Tonbridge and Tunbridge Wells are built on the Hastings Beds.The Weald derives its ancient name from the Germanic word wald meaning simply woodland. Much of the area remains today densely wooded; where there are also heavy clays the tracks through are nearly impassable for much of the year.

The Wealden dome is a Mesozoic structure lying on a Palaeozoic foundation, which usually creates the right conditions for coal formation. This is found in East Kent, roughly between Deal, Canterbury, and Dover. The coal measures within the Westphalian Sandstone are deep (below 244m - 396m) and subject to flooding. They occur in two major troughs, which extend under the English Channel where similar coalfields are sited.Seismic activity has occasionally been recorded in Kent, though the epicentre is offshore. In 1382 and 1580 there were two earthquakes exceeding 6.0 on the Richter Scale. In 1776, 1950, and 28 April 2007 there were earthquakes of around 4.3. The 2007 earthquake caused physical damage in Folkestone.The coastline of Kent is continually changing, due to uplift, sedimentation, and marine erosion. The Isle of Thanet was till recently (AD 960) an island, formed around a deposit of chalk. The channels silted up with alluvium. Similarly Romney Marsh and Dungeness have been formed by accumulation of alluvium.Kent's principal river, the River Medway, rises near Edenbridge and flows some 25 miles (40 km) eastwards to a point near Maidstone, when it turns north. Here it breaks through the North Downs at Rochester before joining the River Thames as its final tributary near Sheerness. The river is tidal as far as Allington lock, but in earlier times cargo-carrying vessels reached as far upstream as Tonbridge. The Medway has captured the head waters of other rivers such as the River Darent. There are other rivers in Kent, most notably the River Stour in the east.

Geology of Denmark

The geology of Denmark includes 12 kilometers of unmetamorphosed sediments lie atop the Precambrian Fennoscandian Shield, the Norwegian-Scottish Caledonides and buried North German-Polish Caledonides. The stable Fennoscandian Shield formed from 1.45 billion years ago to 850 million years ago in the Proterozoic. The Fennoscandian Border Zone is a large fault, bounding the deep basement rock of the Danish Basin—a trough between the Border Zone and the Ringkobing-Fyn High. The Sorgenfrei-Tornquist Zone is a fault-bounded area displaying Cretaceous-Cenozoic inversion.

Geology of Lithuania

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.

Green earth

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.First used by the ancient Romans, green earth has been identified on wall paintings at Pompeii and Dura-Europos. The Renaissance painter and writer Cennino Cennini claimed that “the ancients never gilded except with this green” being used as a bole, or undercoating. In the Middle Ages one of its best-known uses was in the underpainting of flesh tones.High quality deposits can be found in England, France, Cyprus, Germany and at Monte Baldo near Verona in Italy. The color ranges from neutral yellow green to pale greenish gray to dark matte olive green.

Green sand

Green sand may refer to:

Green sand (casting), slightly damp sand, used in sand casting of metals

Greensand, a mineral containing glauconite

Olivine sand, which can form "green sand beaches"

Papakolea Beach, commonly called the Green Sand Beach on the island of Hawaiʻi

Greensand

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.

Hannut Formation

The Hannut Formation (French: Formation de Hannut; Dutch: Formatie van Hannut; abbreviation: Hn) is a geologic formation in the subsurface of northern Belgium. The formation consists of marine clay and silt, alternating with moer sandy layers. On top of this the lithology changes to limestone, siltstone and sandstone and the top of the formation is formed by a layer of glauconite bearing sand. The Hannut Formation was formed during the early to middle Thanetian age (Late Paleocene, about 57 million years ago).

The formation is named after the town of Hannut in the province of Liège.

Illite

Illite is a group of closely related non-expanding clay minerals. Illite is a secondary mineral precipitate, and an example of a phyllosilicate, or layered alumino-silicate. Its structure is a 2:1 sandwich of silica tetrahedron (T) – alumina octahedron (O) – silica tetrahedron (T) layers. The space between this T-O-T sequence of layers is occupied by poorly hydrated potassium cations which are responsible for the absence of swelling. Structurally, illite is quite similar to muscovite with slightly more silicon, magnesium, iron, and water and slightly less tetrahedral aluminium and interlayer potassium. The chemical formula is given as (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)], but there is considerable ion (isomorphic) substitution. It occurs as aggregates of small monoclinic grey to white crystals. Due to the small size, positive identification usually requires x-ray diffraction or SEM-EDS (automated mineralogy) analysis. Illite occurs as an altered product of muscovite and feldspar in weathering and hydrothermal environments; it may be a component of sericite. It is common in sediments, soils, and argillaceous sedimentary rocks as well as in some low grade metamorphic rocks. The iron rich member of the illite group, glauconite, in sediments can be differentiated by x-ray analysis.The cation-exchange capacity (CEC) of illite is smaller than that of smectite but higher than that of kaolinite, typically around 20 – 30 meq/100 g.

Illite was first described for occurrences in the Maquoketa shale in Calhoun County, Illinois, US, in 1937. The name was derived from its type location in Illinois.Illite is also called hydromica or hydromuscovite. Brammallite is a sodium rich analogue. Avalite is a chromium bearing variety which has been described form Mt. Avala, Belgrade, Serbia.

Kokoamu Greensand

The Kokoamu Greensand is a geological formation found in New Zealand. It is a fossil-bearing, late Oligocene, greensand rock unit of the eastern South Island, especially the Waitaki District of North Otago and the southern Canterbury region. The formation was named by geologist Maxwell Gage in the 1950s. In North Otago it underlies the thicker and harder Otekaike Limestone. The formation gets its green colour from the mineral glauconite which forms slowly on the ocean floor.

Pellets (petrology)

Pellets are small spherical to ovoid or rod-shaped grains that are common component of many limestones. They are typically 0.03 to 0.3 mm long and composed of carbonate mud (micrite). Their most common size is 0.04 to 0.08 mm. Pellets typically lack any internal structure and are remarkably uniform in size and shape in any single limestone sample. They consist either of aggregated carbonate mud, precipitated calcium carbonate, or a mixture of both. They either are or were composed either of aragonite, calcite, or a mixture of both. Also, pellets composed of either glauconite or phosphorite are common in marine sedimentary rocks. Pellets occur in Precambrian through Phanerozoic strata. They are an important component mainly in Phanerozoic strata. The consensus among sedimentologists and petrographers is that pellets are the fecal products of invertebrate organisms because of their constant size, shape, and extra-high content of organic matter.Pellets differ from oolites and intraclasts, which are also found in limestones. They differ from oolites in that pellets lack the radial or concentric structures that characterize oolites. They differ from intraclasts in that pellets lack the complex internal structure, which is typical of intraclasts. In addition, pellets, quite unlike intraclasts, are characterized by a remarkable uniformity of shape, extremely good sorting, and small size.By definition, pellets differ from peloids, in that pellets have a specific size, shape, and implied origin—while peloids vary widely in size, shape, and origin. Pellets, in the strict sense, are fecal products of invertebrate organisms. Peloids are allochems of any size, structure, or origin. As a result, peloids not only include possible pellets, but also include a variety of other distinctly non-pellet grains—such as indistinct intraclasts, micritized ooids, or fossil fragments. In addition, some peloids are even microbial or inorganic precipitates. Carbonate geologists consider the vast majority of peloids as secondary allochems created by biological degradation or “micritization” of other primary carbonate grains, i.e., ooids, bioclasts, or pellets.

White Bluff Formation

The White Bluff Formation is a marl, sand, and clay geologic formation in Arkansas that is part of the Jackson Group. It preserves fossils dating back to the Paleogene period, specifically the Eocene.

Winona Formation

The Winona Formation (also called the Winona Sand or the Winona Greensand) is a sand geologic formation in Mississippi. It preserves fossils dating back to the Paleogene period.

Micas
Talcs
Pyrophyllite series
Kaolinites
Serpentines
Corrensites
Smectites and vermiculite family
Chlorites
Allophanes
Sepiolites
Pyrosmalites
Stilpnomelanes

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