[[H-M symbol]]:(2/m 2/m 2/m)"},"symmetry":{"wt":"''Cmcm''"},"unit cell":{"wt":"a = 3.88,b = 12.54
c = 3.07 [Å];Z = 4"},"color":{"wt":"Ruby-red to reddish brown;light reddish to red-orange in transmitted light;gray-white in reflected light"},"colour":{"wt":""},"habit":{"wt":"Flattened scales aggregated into plumose groups and rosettes;massive,bladed to fibrous or micaceous"},"twinning":{"wt":""},"cleavage":{"wt":"{010}Perfect"},"fracture":{"wt":""},"tenacity":{"wt":""},"mohs":{"wt":"5"},"luster":{"wt":"sub metallic"},"streak":{"wt":"Dull orange"},"diaphaneity":{"wt":"Transparent"},"gravity":{"wt":"4"},"density":{"wt":""},"polish":{"wt":""},"opticalprop":{"wt":"Biaxial (−)"},"refractive":{"wt":"nα= 1.940 nβ= 2.200 nγ= 2.510"},"birefringence":{"wt":"δ= 0.570"},"pleochroism":{"wt":"Strong;X = colorless to yellow;Y = orange,yellow,dark red-orange;Z = orange,yellow,darker red-orange"},"2V":{"wt":"Measured:83°"},"dispersion":{"wt":""},"extinction":{"wt":""},"length fast/slow":{"wt":""},"fluorescence":{"wt":""},"absorption":{"wt":""},"melt":{"wt":""},"fusibility":{"wt":""},"diagnostic":{"wt":""},"solubility":{"wt":""},"impurities":{"wt":""},"alteration":{"wt":""},"other":{"wt":""},"prop1":{"wt":""},"prop1text":{"wt":""},"references":{"wt":"[http://webmineral.com/data/Lepidocrocite.shtml Webmineral data][http://www.mindat.org/show.php?id=2379&ld=1&pho= Mindat with locality data][http://www.handbookofmineralogy.com/pdfs/lepidocrocite.pdf Handbook of Mineralogy]"}},"i":0}}]}" id="mwBA">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent}.mw-parser-output .infobox-3cols-child{margin:auto}.mw-parser-output .infobox .navbar{font-size:100%}body.skin-minerva .mw-parser-output .infobox-header,body.skin-minerva .mw-parser-output .infobox-subheader,body.skin-minerva .mw-parser-output .infobox-above,body.skin-minerva .mw-parser-output .infobox-title,body.skin-minerva .mw-parser-output .infobox-image,body.skin-minerva .mw-parser-output .infobox-full-data,body.skin-minerva .mw-parser-output .infobox-below{text-align:center}html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data *{background:#1f1f23!important;color:#f8f9fa}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data *{background:#1f1f23!important;color:#f8f9fa}}
Lepidocrocite | |
---|---|
General | |
Category | Oxide minerals |
Formula (repeating unit) | γ-FeO(OH) |
IMA symbol | Lpc [1] |
Strunz classification | 4.FE.15 |
Crystal system | Orthorhombic |
Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
Space group | Cmcm |
Unit cell | a = 3.88, b = 12.54 c = 3.07 [Å]; Z = 4 |
Identification | |
Formula mass | 88.85 g/mol |
Color | Ruby-red to reddish brown; light reddish to red-orange in transmitted light; gray-white in reflected light |
Crystal habit | Flattened scales aggregated into plumose groups and rosettes; massive, bladed to fibrous or micaceous |
Cleavage | {010} Perfect |
Mohs scale hardness | 5 |
Luster | sub metallic |
Streak | Dull orange |
Diaphaneity | Transparent |
Specific gravity | 4 |
Optical properties | Biaxial (−) |
Refractive index | nα = 1.940 nβ = 2.200 nγ = 2.510 |
Birefringence | δ = 0.570 |
Pleochroism | Strong; X = colorless to yellow; Y = orange, yellow, dark red-orange; Z = orange, yellow, darker red-orange |
2V angle | Measured: 83° |
References | [2] [3] [4] |
Lepidocrocite (γ-FeO(OH)), also called esmeraldite or hydrohematite, is an iron oxide-hydroxide mineral. Lepidocrocite has an orthorhombic crystal structure, a hardness of 5, specific gravity of 4, a submetallic luster and a yellow-brown streak. It is red to reddish brown and forms when iron-containing substances rust underwater. Lepidocrocite is commonly found in the weathering of primary iron minerals and in iron ore deposits. It can be seen as rust scale inside old steel water pipes and water tanks.
The structure of lepidocrocite is similar to the boehmite structure found in bauxite and consists of layered iron(III) oxide octahedra bonded by hydrogen bonding via hydroxide layers. This relatively weakly bonded layering accounts for the scaley habit of the mineral.
It was first described in 1813 from the Zlaté Hory polymetallic ore deposit in Moravia, Czech Republic. The name is from the Greek lipis for scale and krokis for fibre.
Hematite, also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of Fe
2O
3. It has the same crystal structure as corundum (Al
2O
3) and ilmenite (FeTiO
3). With this it forms a complete solid solution at temperatures above 950 °C (1,740 °F).
Hornblende is a complex inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common in igneous and metamorphic rocks.
Limonite is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as FeO(OH)·nH2O, although this is not entirely accurate as the ratio of oxide to hydroxide can vary quite widely. Limonite is one of the three principal iron ores, the others being hematite and magnetite, and has been mined for the production of iron since at least 400 BC.
Goethite is a mineral of the diaspore group, consisting of iron(III) oxide-hydroxide, specifically the α-polymorph. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient times for its use as a pigment. Evidence has been found of its use in paint pigment samples taken from the caves of Lascaux in France. It was first described in 1806 based on samples found in the Hollertszug Mine in Herdorf, Germany. The mineral was named after the German polymath and poet Johann Wolfgang von Goethe (1749–1832).
Chalcopyrite ( KAL-kə-PY-ryte, -koh-) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green-tinged black.
Gibbsite, Al(OH)3, is one of the mineral forms of aluminium hydroxide. It is often designated as γ-Al(OH)3 (but sometimes as α-Al(OH)3). It is also sometimes called hydrargillite (or hydrargyllite).
Chromite is a crystalline mineral composed primarily of iron(II) oxide and chromium(III) oxide compounds. It can be represented by the chemical formula of FeCr2O4. It is an oxide mineral belonging to the spinel group. The element magnesium can substitute for iron in variable amounts as it forms a solid solution with magnesiochromite (MgCr2O4). A substitution of the element aluminium can also occur, leading to hercynite (FeAl2O4). Chromite today is mined particularly to make stainless steel through the production of ferrochrome (FeCr), which is an iron-chromium alloy.
Diaspore – also called diasporite, empholite, kayserite, or tanatarite – is an aluminium hydroxide oxide mineral, α-AlO(OH), crystallizing in the orthorhombic system and isomorphous with goethite. It occurs sometimes as flattened crystals, but usually as lamellar or scaly masses, the flattened surface being a direction of perfect cleavage on which the lustre is markedly pearly in character. It is colorless or greyish-white, yellowish, sometimes violet in color, and varies from translucent to transparent. It may be readily distinguished from other colorless transparent minerals with a perfect cleavage and pearly luster by its greater hardness of 6.5–7. Its specific gravity is 3.4. When heated before the blowpipe, it decrepitates violently, breaking up into white pearly scales.
Bog iron is a form of impure iron deposit that develops in bogs or swamps by the chemical or biochemical oxidation of iron carried in solution. In general, bog ores consist primarily of iron oxyhydroxides, commonly goethite.
Boehmite or böhmite is an aluminium oxide hydroxide mineral, a component of the aluminium ore bauxite. It is dimorphous with diaspore. It crystallizes in the orthorhombic dipyramidal system and is typically massive in habit. It is white with tints of yellow, green, brown or red due to impurities. It has a vitreous to pearly luster, a Mohs hardness of 3 to 3.5 and a specific gravity of 3.00 to 3.07. It is colorless in thin section, optically biaxial positive with refractive indices of nα = 1.644 – 1.648, nβ = 1.654 – 1.657 and nγ = 1.661 – 1.668.
Flowstones are sheetlike deposits of calcite or other carbonate minerals, formed where water flows down the walls or along the floors of a cave. They are typically found in "solution caves", in limestone, where they are the most common speleothem. However, they may form in any type of cave where water enters that has picked up dissolved minerals. Flowstones are formed via the degassing of vadose percolation waters.
Manganite is a mineral composed of manganese oxide-hydroxide, MnO(OH), crystallizing in the monoclinic system (pseudo-orthorhombic). Crystals of manganite are prismatic and deeply striated parallel to their length; they are often grouped together in bundles. The color is dark steel-grey to iron-black, and the luster brilliant and submetallic. The streak is dark reddish brown. The hardness is 4, and the specific gravity is 4.3. There is a perfect cleavage parallel to the brachypinacoid, and less-perfect cleavage parallel to the prism faces. Twinned crystals are not infrequent.
Adamite is a zinc arsenate hydroxide mineral, Zn2AsO4OH. It is a mineral that typically occurs in the oxidized or weathered zone above zinc ore occurrences. Pure adamite is colorless, but usually it possess yellow color due to Fe compounds admixture. Tints of green also occur and are connected with copper substitutions in the mineral structure. Olivenite is a copper arsenate that is isostructural with adamite and there is considerable substitution between zinc and copper resulting in an intermediate called cuproadamite. Zincolivenite is a recently discovered mineral being an intermediate mineral with formula CuZn(AsO4)(OH). Manganese, cobalt, and nickel also substitute in the structure. An analogous zinc phosphate, tarbuttite, is known.
Iron(II) hydroxide or ferrous hydroxide is an inorganic compound with the formula Fe(OH)2. It is produced when iron(II) salts, from a compound such as iron(II) sulfate, are treated with hydroxide ions. Iron(II) hydroxide is a white solid, but even traces of oxygen impart a greenish tinge. The air-oxidised solid is sometimes known as "green rust".
Iron(III) oxide-hydroxide or ferric oxyhydroxide is the chemical compound of iron, oxygen, and hydrogen with formula FeO(OH).
Ferrihydrite (Fh) is a widespread hydrous ferric oxyhydroxide mineral at the Earth's surface, and a likely constituent in extraterrestrial materials. It forms in several types of environments, from freshwater to marine systems, aquifers to hydrothermal hot springs and scales, soils, and areas affected by mining. It can be precipitated directly from oxygenated iron-rich aqueous solutions, or by bacteria either as a result of a metabolic activity or passive sorption of dissolved iron followed by nucleation reactions. Ferrihydrite also occurs in the core of the ferritin protein from many living organisms, for the purpose of intra-cellular iron storage.
Fougèrite is a relatively recently described naturally occurring green rust mineral. It is the archetype of the fougèrite group in the larger hydrotalcite supergroup of naturally occurring layered double hydroxides. The structure is based on brucite-like layers containing Fe2+ and Fe3+ cations, O2− and OH− anions, with loosely bound [CO3]2− groups and H2O molecules between the layers. Fougèrite crystallizes in trigonal system. The ideal formula for fougèrite is [Fe2+4Fe3+2(OH)12][CO3]·3H2O. Higher degrees of oxidation produce the other members of the fougèrite group, namely trébeurdenite, [Fe2+2Fe3+4O2(OH)10][CO3]·3H2O and mössbauerite, [Fe3+6O4(OH)8][CO3]·3H2O.
Laterite is a soil type rich in iron and aluminium and is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of high iron oxide content. They develop by intensive and prolonged weathering of the underlying parent rock, usually when there are conditions of high temperatures and heavy rainfall with alternate wet and dry periods. The process of formation is called laterization. Tropical weathering is a prolonged process of chemical weathering which produces a wide variety in the thickness, grade, chemistry and ore mineralogy of the resulting soils. The majority of the land area containing laterites is between the tropics of Cancer and Capricorn.
Green rust is a generic name for various green crystalline chemical compounds containing iron(II) and iron(III) cations, the hydroxide (HO−
) anion, and another anion such as carbonate (CO2−
3), chloride (Cl−
), or sulfate (SO2−
4), in a layered double hydroxide structure. The most studied varieties are
Hidalgoite, PbAl3(AsO4)(SO4)(OH)4, is a rare member of the beudantite group and is usually classified as part of the alunite family. It was named after the place where it was first discovered, the Zimapán mining district, Hidalgo, Mexico. At Hidalgo where it was initially discovered, it was found as dense white masses in alternating dikes of quartz latite and quartz monzonite alongside other secondary minerals such as sphalerite, arsenopyrite, cerussite and trace amounts of angelsite and alamosite, it was then rediscovered at other locations such as Australia where it occurs on oxidized shear zones above greywacke shales especially on the anticline prospects of the area, and on fine grained quartz-spessartine rocks in Broken Hill, Australia. Hidalgoite specimens are usually associated with copper minerals, clay minerals, iron oxides and polymetallic sulfides in occurrence.