Cyrilovite (NaFe₃³⁺(PO₄)₂(OH)₄·2(H₂O)) is a hydrous sodium iron

phosphate mineral Phosphate minerals are minerals that contain the tetrahedrally coordinated phosphate () anion, sometimes with arsenate () and vanadate () substitutions, along with chloride (Cl−), fluoride (F−), and hydroxide (OH−) anions, that also fit in ...

. It is

isomorphous In mathematics, an isomorphism is a structure-preserving mapping or morphism between two structures of the same type that can be reversed by an inverse mapping. Two mathematical structures are isomorphic if an isomorphism exists between them. ...

and isostructural with

wardite Wardite is a hydrous sodium aluminium phosphate hydroxide mineral with formula: Na Al3( P O4)2(O H)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 ...

, the sodium aluminium counterpart.Lindberg, M. L. (1957) Relationship of the minerals avelinoite, cyrilovite, and wardite. American Mineralogist, 42, 204–213. Cyrilovite is found in

granitic A granitoid is a broad term referring to a diverse group of coarse-grained igneous rocks that are widely distributed across the globe, covering a significant portion of the Earth's exposed surface and constituting a large part of the continental ...

pegmatite A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic c ...

s.Fransolet, A. M., Cooper, M. A., Cerny, P., Hawthorne, C., Chapman, R. (2000) The tanco pegmatite at Bernic Lake, Southeastern Manitoba. The Canadian Mineralogist, 38, 893–898. It was first discovered in 1953 in a pegmatite at Cyrilov, near Velké Meźiřiči, West

Moravia Moravia ( ; ) is a historical region in the eastern Czech Republic, roughly encompassing its territory within the Danube River's drainage basin. It is one of three historical Czech lands, with Bohemia and Czech Silesia. The medieval and early ...

Czech Republic The Czech Republic, also known as Czechia, and historically known as Bohemia, is a landlocked country in Central Europe. The country is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the south ...

.http://www.mindat.org/min-1206.html Mindat.org.

Composition

The chemical formula of cyrilovite is NaFe³⁺₃(PO₄)₂(OH)₄·2(H₂O).http://rruff.geo.arizona.edu/doclib/hom/cyrilovite.pdf Handbook of Mineralogy Parent phosphate minerals,

fluorapatite Fluorapatite, often with the alternate spelling of fluoroapatite, is a phosphate mineral with the formula Ca5(PO4)3F (calcium fluorophosphate). Fluorapatite is a hard crystalline solid. Although samples can have various color (green, brown, blu ...

and

triplite Triplite is a rare phosphate mineral with formula: . It occurs in phosphate-rich granitic pegmatites typically as irregular brown opaque masses. Triplite was first described in 1813 for an occurrence in Chanteloube, Limousin, France.zwieselite, were transformed by

hydrothermal alteration Metasomatism (from the Greek μετά ''metá'' "change" and σῶμα ''sôma'' "body") is the chemical alteration of a Rock (geology), rock by hydrothermal and other fluids. It is traditionally defined as metamorphism which involves a change in t ...

and

weathering Weathering is the deterioration of rocks, soils and minerals (as well as wood and artificial materials) through contact with water, atmospheric gases, sunlight, and biological organisms. It occurs '' in situ'' (on-site, with little or no move ...

to give a complex,

microcrystalline A microcrystalline material is a crystallized substance or rock that contains small crystals visible only through microscopic examination. There is little agreement on the range of crystal sizes that should be regarded as microcrystalline, but ...

intergrowth of secondary phosphate minerals that include cyrilovite.Lottermoser, B., Lu, J. (1997) Petrogenesis of rare-element pegmatites in the Olary Block, South Australia. 1. Mineralogy and chemical evolution. Mineralogy & Petrology, 59, 1–19. The sequence of phosphate transformations ended with the formation of cyrilovite within the fluorapatite fractures and the replacement of fluorapatite by

lipscombite Lipscombite (Fe2+,Mn2+)(Fe3+)2(PO4)2(OH)2 is a green gray, olive green, or black. phosphate-based mineral containing iron, manganese, and iron phosphate. Lipscombite is often formed at meteorite impact sites where its crystals are microscopic ...

and

crandallite Crandallite is a calcium aluminium basic phosphate mineral. It has ideal formula . Crandallite was named after Milan L. Crandall Jr, who worked for Knight Syndicate. This mineral is found in laterite and in alteration products of phosphate rich p ...

-group minerals. Fransolet suggest that a part of the leached Na leads to the

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...

of cyrilovite, in the

fissure A fissure is a long, narrow crack opening along the surface of Earth. The term is derived from the Latin word , which means 'cleft' or 'crack'. Fissures emerge in Earth's crust, on ice sheets and glaciers, and on volcanoes. Ground fissure A ...

s cause by the volume decrease resulting from the transformation of typhylite to heteresoite. Mobilization of

alkalis In chemistry, an alkali (; from the Arabic word , ) is a basic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The a ...

and of relatively immobile elements including aluminium and

rare-earth element The rare-earth elements (REE), also called the rare-earth metals or rare earths, and sometimes the lanthanides or lanthanoids (although scandium and yttrium, which do not belong to this series, are usually included as rare earths), are a set o ...

s are subsequently incorporated into precipitating cyrilovite, lipscombite and crandallite-group minerals. The chemical analysis shows substitution not only of Al for Fe, but also of K and Mn for Na, measured and observed

specific gravities Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

are considered to be in good agreement.

Ferric In chemistry, iron(III) or ''ferric'' refers to the chemical element, element iron in its +3 oxidation number, oxidation state. ''Ferric chloride'' is an alternative name for iron(III) chloride (). The adjective ''ferrous'' is used instead for i ...

iron occurs virtually alone in H₂O rich minerals such as phosphosiderite, and coupled with Na, K, or Ca in cyrilovite. It is soluble in hot dilute

HCl HCL may refer to: Science and medicine * Hairy cell leukemia, an uncommon and slowly progressing B cell leukemia * Harvard Cyclotron Laboratory, from 1961 to 2002, a proton accelerator used for research and development * Hollow-cathode lamp, a s ...

, in hot dilute H₂SO₄, and, with difficulty, in hot dilute HNO₃. In the closed tube, it gives off water and fuses.

Geologic occurrence

The mineral wardite is capable of crystallizing in a similar form to that of cyrilovite because of their closely related chemical compositions. Between wardite's composition, NaAl₃(PO₄)₂(OH)₄·2(H₂O), and cyrilovite's composition, NaFe₃(PO₄)₂(OH)₄·2(H₂O), they are able to form end members of a series of solid solutions. Either of the two minerals can occur in various proportions in a series of solid solutions in the wardite mineral group. Cyrilovite is a rare accessory mineral in some

oxidizing Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...

phosphate-bearing granite pegmatitles and iron deposits. The sequence of phosphate transformations ended with the formation of cyrilovite within the F-apatite factures and the replacement of F-apatite by lipscombite and crandillite-group minerals. Weathering-related cyrilovite, lipscombite, and crandillite-group minerals were formed by percolating meteoric waters under increasing oxygen

fugacity In thermodynamics, the fugacity of a real gas is an effective partial pressure which replaces the mechanical partial pressure in an accurate computation of chemical equilibrium. It is equal to the pressure of an ideal gas which has the same tempe ...

Structure

The crystal structures of natural wardite and of the isomorphous cyrilovite have the

space group In mathematics, physics and chemistry, a space group is the symmetry group of a repeating pattern in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of the pattern that ...

P41212, Z=4). Hydrogen atoms were not located, but reasonable positions can be estimated. The cell dimensions of cyrilovite are: ''c'' = 19.4, ''a'' = 7.32 Å. The individual crystals are usually smaller than 0.1 mm and many of them are intergrown. Crystals are squat and when single tend to lie on the basal pinacoid. The pinacoid and the dipyramid are the dominant forms; all the faces of these forms tend to be present and equally well developed. The dipyramid is not always present. The direction for the a-axis is at 45° angle to the smallest primitive

unit cell In geometry, biology, mineralogy and solid state physics, a unit cell is a repeating unit formed by the vectors spanning the points of a lattice. Despite its suggestive name, the unit cell (unlike a unit vector In mathematics, a unit vector i ...

Physical properties

Cyrilovite is a vitreous translucent mineral that can appear in colors ranging from a bright yellow, honey-yellow, orange to brownish yellow, or brown and it has a

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to plastic deformation, such as an indentation (over an area) or a scratch (linear), induced mechanically either by Pressing (metalworking), pressing or abrasion ...

of 4. It has a yellow streak. The mineral is classified under the space group P4₁2₁2 and is

tetragonal In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the Cube (geometry), cube becomes a rectangular Pri ...

References

{{Reflist *Breitinger, D. K., et al. (2004) Combined vibrational spectra of natural wardite. Journal of Molecular Structure, 706, 95–99. *Cooper, M., Hawthorne, F. C., Cerny, P. (2000) Refinement of the crystal structure of cyrilovite from cyrilov, western Moravia, Czech Republic. Journal of Czech Geological Society, 45, 95–100. Sodium minerals Iron(III) minerals Phosphate minerals