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 and triplite-zwieselite, were transformed by hydrothermal alteration and weathering to give a complex, microcrystalline 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 and crandallite-group minerals. Fransolet suggest that a part of the leached Na leads to the Precipitation (chemistry), precipitation of cyrilovite, in the fracture (geology), fissures cause by the volume decrease resulting from the transformation of typhylite to heteresoite. Mobilization of alkalis and of relatively immobile elements including aluminium and rare-earth elements 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 gravity, specific gravities are considered to be in good agreement. Ferric 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 Hydrochloric acid, HCl, in hot dilute Sulfuric acid, H2SO4, and, with difficulty, in hot dilute Nitric acid, 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 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.Structure
The crystal structures of natural wardite and of the isomorphous cyrilovite have the space group 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 Angstrom, 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 wikt:basal, 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.Physical properties
Cyrilovite is a vitreous lustre, 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 of 4. It has a yellow streak. The mineral is classified under the space group P41212 and is tetragonal.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