Brazilianite

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Brazilianite
Brazilianite-4jg60a.jpg
Brazilianite from type locality, Conselheiro Pena, Minas Gerais, Brazil
General
Category Phosphate minerals
Formula
(repeating unit)		NaAl3(PO4)2(OH)4
sodium aluminium phosphate hydroxide
IMA symbol Bzl [1]
Strunz classification 8.BK.05
Crystal system Monoclinic
Crystal class Prismatic (2/m)
(same H-M symbol)
Space group P21/n
Unit cell a = 11.229 Å,
b = 10.142 Å,
c = 7.098 Å; β = 97.4°; Z = 4
Identification
ColorYellow, green, colorless
Crystal habit Prismatic crystals, may be radially-fibrous or globular druses
Cleavage (010) Distinct to good
Fracture Conchoidal
Mohs scale hardness5.5
Luster Vitreous
Streak White
Diaphaneity Transparent to translucent
Specific gravity 2.98
Optical propertiesBiaxial (+)
Refractive index nα = 1.602 nβ = 1.609 nγ = 1.621 - 1.623
Birefringence δ = 0.019 - 0.021
References [2] [3]

Brazilianite, whose name derives from its country of origin, Brazil, is a typically yellow-green phosphate mineral, most commonly found in phosphate-rich pegmatites.

Contents

It occurs in the form of perfect crystals grouped in druses, in pegmatites, and is often of precious-stone quality. One noted deposit of brazilianite is in the surroundings of Conselheiro Pena, in Minas Gerais, Brazil.

Some of these are found on leaves of muscovite with their strong silvery glitter, ingrown in their parent rock. The crystals, dark greenish-yellow to olive-green, sometimes measure up to 12 cm (4.7 in) in length and 8 cm (3.1 in) in width. Crystals of similar shape and dimensions have been discovered in another deposit in Minas Gerais, near Mantena, but they lack the perfection of the crystal form.[ citation needed ] Many brazilianite specimens found in mineral collections originated from the Palermo and the Charles Davis mines in Grafton County, New Hampshire.

Composition

Brazilianite, NaAl3(PO4)2(OH)4 is a hydrous sodium aluminium phosphate that forms through the metasomatic alteration of amblygonite-montebrasite. [4] Amblygonite, LiAlPO4F in combination with quartz goes through an OH-F exchange to make montebrasite, LiAlPO4{F,OH} at temperatures greater than 480 °C. [4] Natromontebrasite, NaAl(PO4)(OH), is formed when montebrasite does though Li-leaching process and there is a Na cation exchange at temperatures less than 450 °C. [4] Brazilianite concludes this process by forming as natromontebrasite combines with fluorapatite, Ca5(PO4)3F. [5] Due to its formation caused by the amblygonite-montebrasite alteration and the presence of tourmaline in the environment where brazilianite forms, different elements are present in the mineral such as P, Al, Fe, Mn, Ba, Sr, Ca, Mg, Na, K, F, and Cl. [6] There are many substitution possibilities in the brazilianite formula. [7] Besides sodium, being replaced by any other element, iron can replace aluminium, and vanadates or arsenates can replace the phosphates. [7]

Structure

Brazilianite is composed of chains of edge-sharing Al-O octahedra that are linked by P-O tetrahedra with sodium in the cavity of the framework. [8] The crystal structure of brazilianite is a~11.23 Å, b~10.14 Å, c~7.10 Å, β~97.4° and Z = 4. [9] The Al-octahedra has two types of octahedral coordination: trans-AlO4(OH)2 and trans-AlO3(OH)3. [8] The two phosphorus atoms in brazilianite are coordinated in a tetrahedral with four oxygen atoms each. [8] The sodium atom is located within the P-O and Al-O polyhedral in an irregular cavity. [8] The coordination of the sodium is best described as the uncommon seven-coordination. [8] The presence of a hydrogen ion in the same cavity where a sodium ion is causes a repulsion between the two, forcing sodium to one side of the cavity so that is it more coordinated with oxygen than its other side. [8] Gatehouse et al., 1974 [8] described the four remaining hydrogen as being in a chain and contributing to the complexity of the structure but Gatta et al., 2013, [6] gives a well define H-bonding scheme and how these hydrogen items confines in OH groups. One of the hydrogen in brazilianite splits to make a fifth hydrogen. [6] The splitting of this hydrogen has not been explained why it happens but it was shown that it can affect the hydrogen bond configuration. [6] Some of the oxygen atoms in the four OH groups in brazilianite act as donors and some as acceptors of the hydrogen bond. [6] One of these oxygen items is both a donor and acceptor to accommodate the hydrogen that split into two. [6]

Physical properties

Brazilianite is a mineral in the monoclinic system that is part of the point group 2/m and belongs to the space group P21/n. [9] The crystals of brazilianite are elongated and prismatic along [100]. [10] Most common forms that are measured in brazilianite {010}, {110}, { 111}. [11] It displays a perfect cleavage on (010), it is brittle and has a conchoidal fracture. [7] The mineral has a Mohs hardness of 5.5 and was believed it had a specific gravity of 2.94 which was first determined by Pough and Henderson, 1945. With the second occurrence of the mineral, it was determined that the specific gravity of the mineral was actually 2.98. [10] Brazilianite has a vitreous luster, has a white streak, and the mineral is translucent to transparent. [7] The color of brazilianite ranges from dark yellow-green to a pale yellow. [6] Brazilianite begins to lose its color when heated to 200 °C and becomes colorless when it is heated to 300 °C. [11]

Geological occurrence

Brazilianite crystals on muscovite, Galilea mine, Minas Gerais, Brazil Brazilianite with muscovite.jpg
Brazilianite crystals on muscovite, Galilea mine, Minas Gerais, Brazil

Brazilianite is typically found in granite pegmatite and it is often found within the cavities within the pegmatite where quartz, beryl and mica are also found. [7] Different habits of brazilianite have been found in different locations. Brazilianite is often found with muscovite. [6] The Corrego Frio pegmatite where brazilianite is found in Brazil is an altered pegmatite dike that had weathered biotite schist between its walls. [7] In New Hampshire, the pegmatite where the brazilianite was found was made up of 99 percent albite, mica, and quartz. [12] Brazilianite also found with tourmaline and feldspar. [12] The sequence of the mineral formation in the pegmatite in Brazil had not been determined. [12] The sequence of mineral formation in New Hampshire was quartz, brazilianite, apatite, whitlockite, and quartz. [10] During the hydrothermal stage, the pegmatite containing the brazilianite is traversed by a late stage low temperature hydrothermal veins where amblygonite-montebrasite is altered to form brazilianite. [4] Brazilianite has been described from other granite pegmatites in Brazil and the United States. [3] It has also been found in different locations in the world, including Rwanda, Yukon Creek in Canada, Argentina, China, France, and Australia. [3]

Special characteristics

Brazilianite is sometimes used as a gemstone. [13] Brazilianite is relatively new phosphate minerals along with amblygonite, turquoise and apatite that are used as gemstones. [6] Brazilianite is often confused with amblygonite, apatite, chrysoberyl, beryl, and topaz. [14] Even though it was first described in 1945, its discovery was actually in 1944 but it was believed it was chrysoberyl until analysis was done to the mineral indicating a new mineral. [7] The State of Minas Gerais is the largest producer and exporter of gemstones in Brazil and is accountable for 74 percent of the official production which includes brazilianite. [15] It is soft and fragile causing it not to be a popular stone. [7] When brazilianite is heated, it loses it yellow color and becomes colorless. [11]

Related Research Articles

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

Amblygonite is a fluorophosphate mineral, (Li,Na)AlPO4(F,OH), composed of lithium, sodium, aluminium, phosphate, fluoride and hydroxide. The mineral occurs in pegmatite deposits and is easily mistaken for albite and other feldspars. Its density, cleavage and flame test for lithium are diagnostic. Amblygonite forms a series with montebrasite, the low fluorine endmember. Geologic occurrence is in granite pegmatites, high-temperature tin veins, and greisens. Amblygonite occurs with spodumene, apatite, lepidolite, tourmaline, and other lithium-bearing minerals in pegmatite veins. It contains about 10% lithium, and has been utilized as a source of lithium. The chief commercial sources have historically been the deposits of California and France.

<span class="mw-page-title-main">Topaz</span> Silicate mineral

Topaz is a silicate mineral made of aluminum and fluorine with the chemical formula Al2SiO4(F, OH)2. It is used as a gemstone in jewelry and other adornments. Common topaz in its natural state is colorless, though trace element impurities can make it pale blue or golden brown to yellow-orange. Topaz is often treated with heat or radiation to make it a deep blue, reddish-orange, pale green, pink, or purple.

<span class="mw-page-title-main">Pegmatite</span> Igneous rock with very large interlocked crystals

A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than 1 cm (0.4 in) and sometimes greater than 1 meter (3 ft). Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic composition to granite. However, rarer intermediate composition and mafic pegmatites are known.

<span class="mw-page-title-main">Apatite</span> Mineral group, calcium phosphate

Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ion, respectively, in the crystal. The formula of the admixture of the three most common endmembers is written as Ca10(PO4)6(OH,F,Cl)2, and the crystal unit cell formulae of the individual minerals are written as Ca10(PO4)6(OH)2, Ca10(PO4)6F2 and Ca10(PO4)6Cl2.

<span class="mw-page-title-main">Lepidolite</span> Light micas with substantial lithium

Lepidolite is a lilac-gray or rose-colored member of the mica group of minerals with chemical formula K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2. It is the most abundant lithium-bearing mineral and is a secondary source of this metal. It is the major source of the alkali metal rubidium.

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

Wardite is a hydrous sodium aluminium phosphate hydroxide mineral with formula: NaAl3(PO4)2(OH)4·2(H2O). Wardite is of interest for its rare crystallography. It crystallizes in the tetragonal trapezohedral class and is one of only a few minerals in that class. Wardite forms vitreous green to bluish green to white to colorless crystals, with pyramidal {102} or {114} faces and with {001} usually present masses. Also appera as fibrous encrustations. It has a Mohs hardness of 5 and a specific gravity of 2.81–2.87.

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

Lithiophilite is a mineral containing the element lithium. It is lithium manganese(II) phosphate with chemical formula LiMnPO4. It occurs in pegmatites often associated with triphylite, the iron end member in a solid solution series. The mineral with intermediate composition is known as sicklerite and has the chemical formula Li(Mn,Fe)PO4). The name lithiophilite is derived from the Greek philos (φιλός) "friend", as lithiophilite is usually found with lithium.

<span class="mw-page-title-main">Phosphate mineral</span> Nickel–Strunz 9 ed mineral class number 8 (isolated tetrahedral units, mainly)

Phosphate minerals are minerals that contain the tetrahedrally coordinated phosphate (PO43−) anion, sometimes with arsenate (AsO43−) and vanadate (VO43−) substitutions, along with chloride (Cl−), fluoride (F−), and hydroxide (OH−) anions, that also fit into the crystal structure.

<span class="mw-page-title-main">Sodium monofluorophosphate</span> Chemical compound

Sodium monofluorophosphate, commonly abbreviated SMFP, is an inorganic compound with the chemical formula Na2PO3F. Typical for a salt, SMFP is odourless, colourless, and water-soluble. This salt is an ingredient in some toothpastes.

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

Whitlockite is a mineral, an unusual form of calcium phosphate. Its formula is Ca9(MgFe)(PO4)6PO3OH. It is a relatively rare mineral but is found in granitic pegmatites, phosphate rock deposits, guano caves and in chondrite meteorites. It was first described in 1941 and named for Herbert Percy Whitlock (1868–1948), American mineralogist and curator at the American Museum of Natural History in New York City.

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

Zanazziite is a complex hydrated phosphate mineral from the roscherite group. It is a magnesium beryllium phosphate mineral. Zanazziite arises as barrel-shaped crystals and can reach up to 4 mm. It grows alongside quartz minerals. It is found in the crevices of Lavra da Ilha pegmatite, near Taquaral, in northeastern Minas Gerais, Brazil. Zanazziite is named after Pier F. Zanazzi. Zanazziite has an ideal chemical formula of Ca2Mg5Be4(PO4)6(OH)4·6H2O.

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

Eosphorite is a brown (occasionally pink) manganese hydrous phosphate mineral with chemical formula: MnAl(PO4)(OH)2·H2O. It is used as a gemstone.

Xanthoxenite is a rare calcium iron(III) phosphate mineral with formula: Ca4Fe3+2(PO4)4(OH)2·3H2O. It occurs as earthy pale to brownish yellow incrustations and lath shaped crystals. It crystallizes in the triclinic crystal system. It occurs as an alteration product of triphylite in pegmatites. It occurs associated with apatite, whitlockite, childrenite–eosphorite, laueite, strunzite, stewartite, mitridatite, amblygonite and siderite.

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

Cyrilovite (NaFe33+(PO4)2(OH)4·2(H2O)) is a hydrous sodium iron phosphate mineral. It is isomorphous and isostructural with wardite, the sodium aluminium counterpart.

<span class="mw-page-title-main">Hureaulite</span> Manganese phosphate mineral

Hureaulite is a manganese phosphate with the formula Mn2+5(PO3OH)2(PO4)2·4H2O. It was discovered in 1825 and named in 1826 for the type locality, Les Hureaux, Saint-Sylvestre, Haute-Vienne, Limousin, France. It is sometimes written as huréaulite, but the IMA does not recommend this for English language text.

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

Whiteite is a rare hydrated hydroxyphosphate mineral.

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

Maricite or marićite is a sodium iron phosphate mineral (NaFe2+PO4), that has two metal cations connected to a phosphate tetrahedron. It is structurally similar to the much more common mineral olivine. Maricite is brittle, usually colorless to gray, and has been found in nodules within shale beds often containing other minerals.

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

Väyrynenite is a rare phosphate mineral with formula MnBe(PO4)(OH,F). It was first described in 1954 for an occurrence in Viitaniemi, Erajarvi, Finland and named for mineralogist Heikki Allan Väyrynen of Helsinki, Finland.

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

Serrabrancaite is a mineral with the chemical formula MnPO4•H2O and which is named for the locality where it was found, the Alto Serra Branca Pegmatite. The Alto Serra Branca mine has been in operation since the 1940s. It is located in Paraiba, Brazil near a village named Pedra Lavrada. Tantalite is the main mineral mined here. Specimens of serrabrancaite are kept in the Mineralogical Collections of both the Bergakademie Freiberg, Germany and the Martin-Luther Universität Halle, Institut für Geologische Wissenschaften.

The phosphate sulfates are mixed anion compounds containing both phosphate and sulfate ions. Related compounds include the arsenate sulfates, phosphate selenates, and arsenate selenates.

References

  1. ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi: 10.1180/mgm.2021.43 . S2CID   235729616.
  2. ↑ Brazilianite data on Webmineral
  3. 1 2 3 Brazilianite on Mindat.org
  4. 1 2 3 4 Baldwin, J.R.; Hill, P. G.; Von Knorring, O.; Oliver, G. J. H. (2000). "Exotic aluminium phosphates, natromontebrasite, brazilianite, goyazite, gorceixite and crandallite from rare-element pegmatites in Namibia". Mineralogical Magazine. 64 (6): 1147–1164. Bibcode:2000MinM...64.1147B. doi:10.1180/002646100549940. ISSN   0026-461X. S2CID   128836092.
  5. ↑ Scholz, R.; Karfunkel, J.; Bermanec, V.; Magela, G.; da Costa, A. H. H.; Souza, L. A. C.; Bilal, E. (2008). "Amblygonite-montebrasite from Divino das Laranjeiras Mendes Pimentel pegmatitic swarm, Minas Gerais, Brasil. II. Mineralogy". Romanian Journal of Mineral Deposits. 83.
  6. 1 2 3 4 5 6 7 8 9 Gatta, G.D.; Vignola, P.; Meven, M.; Rinaldi, R. (2013). "Neutron diffraction in gemology: Single-crystal diffraction study of brazilianite, NaAl3(PO4)2(OH)4". American Mineralogist. 98 (8–9): 1624–1630. Bibcode:2013AmMin..98.1624G. doi:10.2138/am.2013.4476. S2CID   100999379.
  7. 1 2 3 4 5 6 7 8 Pough, F.H; Henderson, E. P (1945). "Brazilianite, a new phosphate mineral". American Mineralogist. 30.
  8. 1 2 3 4 5 6 7 Gatehouse, B.M.; Miskin, B. K. (1974). "The crystal structure of brazilianite, NaAl3 (PO4)2(OH)4". Acta Crystallographica Section B. 30 (5): 1311–1317. doi:10.1107/s0567740874004730.
  9. 1 2 Frost, R.L.; Xi, Y (2012). "Molecular structure of the phosphate mineral brazilianite NaAl3(PO4)2(OH)4-A semi-precious jewel" (PDF). Journal of Molecular Structure. 1010: 179–183. Bibcode:2012JMoSt1010..179F. doi:10.1016/j.molstruc.2011.12.003. S2CID   91695205.
  10. 1 2 3 Frondel, C.; Lindberg, M.L. (1948). "Second occurrence of brazilianite". American Mineralogist. 33.
  11. 1 2 3 Čobić, A.; Zebec, V.; Scholz, R.; Bermanec, V.; de Brito Barreto, S. (2011). "Crystal morphology and xrd peculiarities of brazilianite from different localities". Natura Croatica. 20 (1).
  12. 1 2 3 Pecora and Fahey, The Corrego Frio Pegmatite, Minas Gerais: Scorzalite and Souzalite, Two New Phosphate Minerals, (1949) American Mineralogist: 34: 83
  13. ↑ Firefly Guide to Gems By Cally Oldershaw
  14. ↑ "Brazilianite gem". Gemstoneindex.net. Archived from the original on 2013-12-19. Retrieved 2013-10-21.
  15. ↑ De Brito Barreto, S.; Bittar, S. M. B. (2010). "The gemstone deposits of Brazil: occurrences, production and economic impact". Boletín de la Sociedad Geológica Mexicana. 62 (1).
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