Vanadinite

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Vanadinite
Vanadinite - ACF mine, Mibladen, Morocco.jpg
General
Category Vanadate minerals
Apatite group
Formula
(repeating unit)
Pb5(VO4)3Cl
IMA symbol Vna [1]
Strunz classification 8.BN.05
Crystal system Hexagonal
Crystal class Dipyramidal (6/m)
H-M symbol: (6/m)
Space group P63/m
Unit cell a = 10.3174,
c = 7.3378 [Å]; Z = 2
Identification
Formula mass 1416.27 g/mol
ColourBright red, orange-red, red-brown, brown, yellow, whitish, grey or colourless or weakly tinted in transmitted light; pale straw-yellow;. may be concentrically zoned
Crystal habit Prismatic or nodular; may be acicular, hairlike, fibrous; rarely rounded, globular
Cleavage None
Fracture Uneven to conchoidal
Tenacity Brittle
Mohs scale hardness3–4
Lustre Resinous to sub-adamantine
Streak brownish yellow
Diaphaneity Transparent, translucent or opaque
Specific gravity 6.8–7.1 (measured) 6.95 (calculated)
Optical propertiesUniaxial (−)
Refractive index nω = 2.416, nε = 2.350
Birefringence δ = 0.066
Ultraviolet fluorescence None
Melting point 3,470 °F (1,910 °C)
References [2] [3] [4]

Vanadinite is a mineral belonging to the apatite group of phosphates, with the chemical formula Pb 5(V O 4)3 Cl. It is one of the main industrial ores of the metal vanadium and a minor source of lead. A dense, brittle mineral, it is usually found in the form of red hexagonal crystals. It is an uncommon mineral, formed by the oxidation of lead ore deposits such as galena. First discovered in 1801 in Mexico, vanadinite deposits have since been unearthed in South America, Europe, Africa, and North America.

Contents

Origins

Vanadinite is an uncommon mineral, only occurring as the result of chemical alterations to a pre-existing material. It is therefore known as a secondary mineral. It is found in arid climates and forms by oxidation of primary lead minerals. Vanadinite is especially found in association with the lead sulfide, galena. Other associated minerals include wulfenite, limonite, and barite. [3] [5]

It was originally discovered in Mexico by the Spanish mineralogist Andrés Manuel del Río in 1801. He called the mineral "brown lead" and asserted that it contained a new element, which he first named pancromium and later, erythronium. However, he was later led to believe that this was not a new element but merely an impure form of chromium. In 1830, Nils Gabriel Sefström discovered a new element, which he named vanadium. It was later revealed that this was identical to the metal discovered earlier by Andrés Manuel del Río. Del Río's "brown lead" was also rediscovered, in 1838 in Zimapan, Hidalgo, Mexico, and was named vanadinite because of its high vanadium content. Other names that have since been given to vanadinite are johnstonite and lead vanadate. [6]

Occurrence

Vanadinite occurs as a secondary mineral in the oxidized zone of lead-bearing deposits; the vanadium is leached from wall-rock silicates. Associated minerals include mimetite, pyromorphite, descloizite, mottramite, wulfenite, cerussite, anglesite, calcite, barite, and various iron oxide minerals. [4]

Deposits of vanadinite are found worldwide including Austria, Spain, Scotland, the Ural Mountains, South Africa, Namibia, Morocco, Argentina, Mexico, and four states of the United States: Arizona, Colorado, New Mexico, and South Dakota. [3] [5] [7]

Vanadinite deposits are found in over 400 mines across the world. Notable vanadinite mines include those at Mibladen and Touisset in Morocco; Tsumeb, Namibia; Cordoba, Argentina; and Sierra County, New Mexico, and Gila County, Arizona, in the United States. [8]

Structure

Vanadinite is a lead chlorovanadate with the chemical formula Pb5(VO4)3Cl. It is composed (by weight) of 73.15% lead, 10.79% vanadium, 13.56% oxygen, and 2.50% chlorine. Each structural unit of vanadinite contains a chlorine ion surrounded by six divalent lead ions at the corners of a regular octahedron, with one of the lead ions provided by an adjoining vanadinite molecule. The distance between each lead and chlorine ion is 317  picometres. The shortest distance between each lead ion is 4.48 Å. The octahedron shares two of its opposite faces with that of neighbouring vanadinite units, forming a continuous chain of octahedrons. Each vanadium atom is surrounded by four oxygen atoms at the corners of an irregular tetrahedron. The distance between each oxygen and vanadium atom is either 1.72 or 1.76 Å. Three oxygen tetrahedrons adjoin each of the lead octahedrons along the chain. [2] [9] [10]

Vanadinite-xtal-2x2x2-centroid-fit-3D-bs-17.png
Crystal packing
Vanadinite-xtal-Cl-coordination-3D-bs-17.png
Chloride coordination sphere
Vanadinite-xtal-Pb1-coordination-3D-bs-17.png
Lead #1 coordination sphere
Vanadinite-xtal-Pb2-coordination-3D-bs-17.png
Lead #2 coordination sphere
Vanadinite-xtal-V-coordination-3D-bs-17.png
Vanadium coordination sphere

Crystals of vanadinite conform to a hexagonal system of symmetry. This internal structure is often reflected in the hexagonal external shape of the crystals. The crystals are usually in the form of short hexagonal prisms, but can also be found as hexagonal pyramids, rounded masses or crusts. A unit cell of vanadinite, the smallest divisible unit that possesses the same symmetry and properties, is in the form of a hexagonal prism. The unit cell of vanadinite is composed of two of its molecules and has the dimensions a = 10.331  Å and c = 7.343 Å, where a is the length of each side of the hexagon and c is the height of the prism. The volume of each unit cell of vanadinite, given by the formula V = a2c sin(60°), is 678.72 Å3. [2] [5]

Characteristics

Vanadinite is in the apatite group of phosphates, and forms a chemical series with the minerals pyromorphite (Pb5(PO4)3Cl) and mimetite (Pb5(AsO4)3Cl), with both of which it may form solid solutions. Whereas most chemical series involve the substitution of metallic ions, this series substitutes its anion groups; phosphate (PO4), arsenate (AsO4) and vanadate (VO4). Common impurities of vanadinite include phosphorus, arsenic and calcium, where these may act as an isomorphic substitute for vanadium (in the first two cases) or lead (in the second). Vanadinite when containing a high amount of the arsenic impurity is known as endlichite. [3] [5]

Vanadinite is usually bright-red or orange-red in colour, although sometimes brown, red-brown, grey, yellow, or colourless. Its distinctive colour makes it popular among mineral collectors. Its streak can be either pale yellow or brownish-yellow. Vanadinite may be transparent, translucent or opaque, and its lustre can range from resinous to adamantine. Vanadinite is anisotropic, meaning that some of its properties differ when measured along different axes. When measured perpendicular and parallel to its axis of anisotropy, its refractive indices are 2.350 and 2.416 respectively. This gives it a birefringence of 0.066. [2] [3] [5]

Vanadinite is very brittle, producing small, conchoidal fragments when fractured. Its hardness is 3–4 on the Mohs scale, about the same as a copper coin. Vanadinite is particularly heavy for a translucent mineral. It has a molar mass of 1416.27  g/mol and its specific gravity can range between 6.6 and 7.2 because of impurities. [3] [5] [7]

Uses

Along with carnotite and roscoelite, vanadinite is one of the main industrial ores of the element vanadium, which can be extracted by roasting and smelting. Vanadinite is also occasionally used as a source of lead. A common process for extracting the vanadium begins with the heating of vanadinite with salt (NaCl) or sodium carbonate (Na2CO3) at about 850 °C to produce sodium vanadate (NaVO3). This is dissolved in water and then treated with ammonium chloride to give an orange-coloured precipitate of ammonium metavanadate. This is then melted to form a crude form of vanadium pentoxide (V2O5). Reduction of vanadium pentoxide with calcium gives pure vanadium. [11]

See also

Related Research Articles

<span class="mw-page-title-main">Muscovite</span> Hydrated phyllosilicate mineral

Muscovite (also known as common mica, isinglass, or potash mica) is a hydrated phyllosilicate mineral of aluminium and potassium with formula KAl2(AlSi3O10)(F,OH)2, or (KF)2(Al2O3)3(SiO2)6(H2O). It has a highly perfect basal cleavage yielding remarkably thin laminae (sheets) which are often highly elastic. Sheets of muscovite 5 meters × 3 meters (16.5 feet × 10 feet) have been found in Nellore, India.

<span class="mw-page-title-main">Vanadium</span> Chemical element, symbol V and atomic number 23

Vanadium is a chemical element; it has symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer (passivation) somewhat stabilizes the free metal against further oxidation.

Alforsite is a barium phosphate chloride mineral with formula: Ba5(PO4)3Cl. It was discovered in 1981, and named to honor geologist John T. Alfors (1930–2005) of the California Geological Survey for his work in the area where it was discovered.

<span class="mw-page-title-main">Wulfenite</span> Molybdate mineral

Wulfenite is a lead molybdate mineral with the formula PbMoO4. It can be most often found as thin tabular crystals with a bright orange-red to yellow-orange color, sometimes brown, although the color can be highly variable. In its yellow form it is sometimes called "yellow lead ore".

<span class="mw-page-title-main">Pyromorphite</span>

Pyromorphite is a mineral species composed of lead chlorophosphate: Pb5(PO4)3Cl, sometimes occurring in sufficient abundance to be mined as an ore of lead. Crystals are common, and have the form of a hexagonal prism terminated by the basal planes, sometimes combined with narrow faces of a hexagonal pyramid. Crystals with a barrel-like curvature are not uncommon. Globular and reniform masses are also found. It is part of a series with two other minerals: mimetite (Pb5(AsO4)3Cl) and vanadinite (Pb5(VO4)3Cl), the resemblance in external characters is so close that, as a rule, it is only possible to distinguish between them by chemical tests. They were formerly confused under the names green lead ore and brown lead ore (German: Grünbleierz and Braunbleierz).

<span class="mw-page-title-main">Mimetite</span> Lead arsenate chloride mineral

Mimetite is a lead arsenate chloride mineral (Pb5(AsO4)3Cl) which forms as a secondary mineral in lead deposits, usually by the oxidation of galena and arsenopyrite. The name derives from the Greek Μιμητής mimetes, meaning "imitator" and refers to mimetite's resemblance to the mineral pyromorphite. This resemblance is not coincidental, as mimetite forms a mineral series with pyromorphite (Pb5(PO4)3Cl) and with vanadinite (Pb5(VO4)3Cl). Notable occurrences are Mapimi, Durango, Mexico and Tsumeb, Namibia.

<span class="mw-page-title-main">Descloizite</span> Mineral

Descloizite is a rare mineral species consisting of basic lead and zinc vanadate, (Pb, Zn)2(OH)VO4, crystallizing in the orthorhombic crystal system and isomorphous with olivenite. Appreciable gallium and germanium may also be incorporated into the crystal structure.

<span class="mw-page-title-main">Vanadate</span> Coordination complex of vanadium

In chemistry, a vanadate is an anionic coordination complex of vanadium. Often vanadate refers to oxoanions of vanadium, most of which exist in its highest oxidation state of +5. The complexes [V(CN)6]3− and [V2Cl9]3− are referred to as hexacyanovanadate(III) and nonachlorodivanadate(III), respectively.

<span class="mw-page-title-main">Ammonium metavanadate</span> Chemical compound

Ammonium metavanadate is the inorganic compound with the formula NH4VO3. It is a white salt, although samples are often yellow owing to impurities of V2O5. It is an important intermediate in the purification of vanadium.

In ore deposit geology, supergene processes or enrichment are those that occur relatively near the surface as opposed to deep hypogene processes. Supergene processes include the predominance of meteoric water circulation (i.e. water derived from precipitation) with concomitant oxidation and chemical weathering. The descending meteoric waters oxidize the primary (hypogene) sulfide ore minerals and redistribute the metallic ore elements. Supergene enrichment occurs at the base of the oxidized portion of an ore deposit. Metals that have been leached from the oxidized ore are carried downward by percolating groundwater, and react with hypogene sulfides at the supergene-hypogene boundary. The reaction produces secondary sulfides with metal contents higher than those of the primary ore. This is particularly noted in copper ore deposits where the copper sulfide minerals chalcocite (Cu2S), covellite (CuS), digenite (Cu18S10), and djurleite (Cu31S16) are deposited by the descending surface waters.

<span class="mw-page-title-main">Wakefieldite</span> Rare-earth mineral series

Wakefieldite is an uncommon rare-earth element vanadate mineral. There are four main types described of wakefieldite- wakefieldite-(La), wakefieldite-(Ce), wakefieldite-(Nd), and wakefieldite-(Y), depending upon the dominant rare-earth metal ion present. Wakefieldite has a Mohs hardness ranging from 4 to 5. Wakefieldite forms crystals of tetragonal structure. In terms of crystal structure, it is the vanadate analog of the rare-earth phosphate mineral xenotime. Unlike xenotime, it is more favorable for wakefieldite to contain the lighter rare-earth elements over the heavier ones. Due to the lanthanide contraction, the heavier rare earths have smaller ionic radii than the lighter ones. When the phosphate anion is replaced by the larger vanadate anion, the tetragonal crystal system preferentially accommodates the larger light rare-earth elements.

<span class="mw-page-title-main">Zemannite</span>

Zemannite is a very rare oxide mineral with the chemical formula Mg0.5ZnFe3+[TeO3]3·4.5H2O. It crystallizes in the hexagonal crystal system and forms small prismatic brown crystals. Because of the rarity and small crystal size, zemannite has no applications and serves as a collector's item.

<span class="mw-page-title-main">Tsumebite</span>

Tsumebite is a rare phosphate mineral named in 1912 after the locality where it was first found, the Tsumeb mine in Namibia, well known to mineral collectors for the wide range of minerals found there. Tsumebite is a compound phosphate and sulfate of lead and copper, with hydroxyl, formula Pb2Cu(PO4)(SO4)(OH). There is a similar mineral called arsentsumebite, where the phosphate group PO4 is replaced by the arsenate group AsO4, giving the formula Pb2Cu(AsO4)(SO4)(OH). Both minerals are members of the brackebuschite group.

<span class="mw-page-title-main">Dicopper chloride trihydroxide</span> Chemical compound

Dicopper chloride trihydroxide is the chemical compound with the formula Cu2(OH)3Cl. It is often referred to as tribasic copper chloride (TBCC), copper trihydroxyl chloride or copper hydroxychloride. It is a greenish crystalline solid encountered in mineral deposits, metal corrosion products, industrial products, art and archeological objects, and some living systems. It was originally manufactured on an industrial scale as a precipitated material used as either a chemical intermediate or a fungicide. Since 1994, a purified, crystallized product has been produced at the scale of thousands of tons per year, and used extensively as a nutritional supplement for animals.

The Tabataud Quarry is situated in the northwestern French Massif Central. The quarry used to be mined for its granodiorite.

<span class="mw-page-title-main">Tarbuttite</span> Phosphate mineral

Tarbuttite is a rare phosphate mineral with formula Zn2(PO4)(OH). It was discovered in 1907 in what is now Zambia and named for Percy Coventry Tarbutt.

<span class="mw-page-title-main">Mottramite</span>

Mottramite is an orthorhombic anhydrous vanadate hydroxide mineral, PbCu(VO4)(OH), at the copper end of the descloizite subgroup. It was formerly called cuprodescloizite or psittacinite (this mineral characterized in 1868 by Frederick Augustus Genth). Duhamelite is a calcium- and bismuth-bearing variety of mottramite, typically with acicular habit.

<span class="mw-page-title-main">Gottlobite</span>

Gottlobite, CaMg(VO4,AsO4)(OH), is a mineral found as isolated crystals or isometric grains of orange or orange-brown color. The size of the crystals are a half millimeter in diameter and are part of the orthorhombic crystal system. Gottlobite forms a solid solution with adelite, which is an end member composition of CaMg(VO4)(OH), as well as being classified in the adelite group. Gottlobite is also part of the vanadates and arsenates group. With these characteristics, it is similar to the minerals tangeite and austinite by X-ray diffraction methods.

<span class="mw-page-title-main">Paramontroseite</span>

Paramontroseite (V4+O2) is a relatively rare orthorhombic vanadium oxide mineral in the Ramsdellite group. Synthetic paramontroseite may have applications in medicine, batteries and electronics.

<span class="mw-page-title-main">Arsendescloizite</span> Lead-zinc mineral

Arsendescloizite is a lead-zinc mineral, approved by the IMA in 1982. It is an arsenate analog of descloizite. Its first description was published in 1982.

References

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  3. 1 2 3 4 5 6 "Vanadinite". MinDat.org. Retrieved 9 June 2007.
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  5. 1 2 3 4 5 6 Treasures of the Earth: The Minerals and Gemstone Collection – Vanadinite factsheet. Orbis Publishing Ltd. 1995.
  6. J. A. Pérez-Bustamante de Monasterio (1990). "Highlights of Spanish chemistry at the time of the chemical revolution of the 18th century". Fresenius' Journal of Analytical Chemistry. 337 (2): 225–228. doi:10.1007/BF00322401. S2CID   197594307.
  7. 1 2 Spencer, Leonard James (1911). "Vanadinite"  . In Chisholm, Hugh (ed.). Encyclopædia Britannica . Vol. 27 (11th ed.). Cambridge University Press.
  8. "Vanadinite". Minerals.net. Retrieved 26 June 2007.
  9. J. Trotter & W. H. Barnes (1958). "The Structure of Vanadinite" (PDF). The Canadian Mineralogist. Retrieved 26 June 2007.
  10. Dai, Yongshan; Hughes, John M. (1989). "Crystal structure refinements of vanadinite and pyromorphite" (PDF). Can. Mineral. 27 (2): 189–192.
  11. Donal O'Leary (2000). "Vanadium". University College Cork. Archived from the original on 5 February 2017. Retrieved 26 June 2007.