Cesanite is the end member of the

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of Hydroxide, OH−, Fluoride, F− and Chloride, Cl− ion, respectively, in the crystal. The formula of the admixture of ...

- wilkeite- ellestadite series that substitutes all of apatite's

phosphate Phosphates are the naturally occurring form of the element phosphorus. In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthop ...

ions An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

with

sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...

ions and balances the difference in charge by replacing several

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

ions with

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

ions. Currently very few sites bearing cesanite have been found and are limited to a geothermal field in Cesano,

Italy Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land b ...

from which its name is derived, Măgurici Cave in

Romania Romania is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to ...

, and in the

San Salvador Island San Salvador Island, previously Watling's Island, is an islands of the Bahamas, island and districts of The Bahamas, district of The Bahamas, famed for being the probable location of Christopher Columbus's first landing of the Americas on 12 Oc ...

cave Caves or caverns are natural voids under the Earth's Planetary surface, surface. Caves often form by the weathering of rock and often extend deep underground. Exogene caves are smaller openings that extend a relatively short distance undergrou ...

s in the

Bahamas The Bahamas, officially the Commonwealth of The Bahamas, is an archipelagic and island country within the Lucayan Archipelago of the Atlantic Ocean. It contains 97 per cent of the archipelago's land area and 88 per cent of its population. ...

History

Cesanite was first discovered in 1981 while the Italian National Electricity Board was doing exploratory drilling to examine a reservoir of heated

brine Brine (or briny water) is a high-concentration solution of salt (typically sodium chloride or calcium chloride) in water. In diverse contexts, ''brine'' may refer to the salt solutions ranging from about 3.5% (a typical concentration of seawat ...

to determine its potential as a

geothermal energy Geothermal energy is thermal energy extracted from the crust (geology), crust. It combines energy from the formation of the planet and from radioactive decay. Geothermal energy has been exploited as a source of heat and/or electric power for m ...

source. When it was first found it was thought to be an apatite until after more thorough examination.

Structure

Cesanite was originally determined by Tazzoli (1983) to be isotypic to that of

hydroxylapatite Hydroxyapatite ( IMA name: hydroxylapatite) (Hap, HAp, or HA) is a naturally occurring mineral form of calcium apatite with the formula , often written to denote that the crystal unit cell comprises two entities. It is the hydroxyl endmembe ...

. This was determined by refining the original

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 ...

dimensions and comparing them to the atomic coordinates of Holly Springs hydroxylapatite. From this it was extrapolated that although different elements are substituted for cesanite, the structure and cell parameters are nearly the same with some differences in the

bond length In molecular geometry, bond length or bond distance is defined as the average distance between Atomic nucleus, nuclei of two chemical bond, bonded atoms in a molecule. It is a Transferability (chemistry), transferable property of a bond between at ...

s of the

tetrahedra In geometry, a tetrahedron (: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular Face (geometry), faces, six straight Edge (geometry), edges, and four vertex (geometry), vertices. The tet ...

.Tazzoli V., (1983) The Crystal-structure of ceanite, CA1+XNA4-X(SO4)3(OH)X.(1-X)H2O, a sulfate isotypic to apatite. Mineralogical Magazine, 47, 59-63. This similarity was to confirm 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 ...

''P''3/m previously assigned to cesanite, this changed in 2002 after a reexamination of cesanite by Piotrowski et al. was prompted by its similarities to a synthetically produced

analog Analog or analogue may refer to: Computing and electronics * Analog signal, in which information is encoded in a continuous variable ** Analog device, an apparatus that operates on analog signals *** Analog electronics, circuits which use analog ...

. After this study it was found that the

crystal structure In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...

of cesanite to be

isostructural Isostructural chemical compounds have similar chemical structures. " Isomorphous" when used in the relation to crystal structures is not synonymous: in addition to the same atomic connectivity that characterises isostructural compounds, isomorphous ...

to this

synthetic Synthetic may refer to: Science * Synthetic biology * Synthetic chemical or compound, produced by the process of chemical synthesis * Synthetic elements, chemical elements that are not naturally found on Earth and therefore have to be created in ...

analog with the chemical formula Ca₂Na₃ OH)(SO₄)₃ What can be inferred from this is that while hydroxylapatite remains similar in its chemical formula it is not longer to be considered a structural analog. The new correct space group is ''P''. It can be inferred that the reason the mistake went unnoticed for so long is that cesanite retains pseudo-symmetry in the array of its tetrahedra that closely mimics ''P''3/m. Cesanite's crystal structure is made up of tetrahedra of

sulfide Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...

cations An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

surrounded by

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

anions An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

distributed along with

hydroxide Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It ...

ions around the Ca and Na ions occupying the M1 through four sites. The M1 and M2 cites create distorted

pentagonal In geometry, a pentagon () is any five-sided polygon or 5-gon. The sum of the internal angles in a simple pentagon is 540°. A pentagon may be simple or self-intersecting. A self-intersecting ''regular pentagon'' (or ''star pentagon'') is cal ...

bipyramids In geometry, a bipyramid, dipyramid, or double pyramid is a polyhedron formed by fusing two pyramids together base-to-base. The polygonal base of each pyramid must therefore be the same, and unless otherwise specified the base vertices are usu ...

while the M3 and M4 create tricapped

trigonal In crystallography, the hexagonal crystal family is one of the six crystal family, crystal families, which includes two crystal systems (hexagonal and trigonal) and two lattice systems (hexagonal and rhombohedral). While commonly confused, the tr ...

prisms. The M3 and M4

polyhedra In geometry, a polyhedron (: polyhedra or polyhedrons; ) is a three-dimensional figure with flat polygonal faces, straight edges and sharp corners or vertices. The term "polyhedron" may refer either to a solid figure or to its boundary su ...

share faces when they are next to each other and form columns parallel to 01while isolated sulfate tetrahedra alternate along the c axis.

Physical properties

Cesanite veins are massive in habit and appear white in color with a silky luster. Individual crystals are colorless and transparent to translucent with a greasy luster. These crystals are elongated and begin with a pyramid on {101*0} that is distorted by a flatting that occurs down the length of the crystal which then extends down with two parallel faces until they are cut off by either a pinacoid or another pyramid. According to the newest sources the unit-cell parameters of cesanite are ''a'' = 9.4630 and ''c'' = 6.9088 Å. In thin section cesanite remains transparent and has moderate

birefringence Birefringence, also called double refraction, is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are described as birefrin ...

. In addition to is structure at room temperature, cesanite exhibits different crystal structures at different temperatures. Polymorphs occur at 425, 625, and 740 °C. These different forms are cause by expansion along the crystallographic axises as cesanite is heated.Deganello S., Artioli G. (1982) Thermal expansion of cesanite between 22 °C and 390 °C. Nues jahrbuch für Mineralogie, Monatshefte, 12, 565-568.

Geologic occurrence

Cesanite has been found in only three places to date. The original occurrence was observed as part of a

fracture Fracture is the appearance of a crack or complete separation of an object or material into two or more pieces under the action of stress (mechanics), stress. The fracture of a solid usually occurs due to the development of certain displacemen ...

sealing process where cesanite

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

s grew to fill in the void. It was found growing in a loosely packed vein of small crystals that became intergrown with those of the neighboring görgeyite crystals. Further occurrences have been noticed in several caves. First in 2001 inside of Lighthouse Cave located on San Salvador Island filling in gaps in

corroded Corroded is a heavy metal band from Ånge, Sweden. The band is best known for their song ''Time And Again'', which was the theme song for the Swedish 2009 ''Survivor'' television series on TV4. The band's second album ''Exit to Transfer'', rel ...

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate Hydrate, dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk ...

and in 2003 inside Măgurici Cave in Romania it was found in close association with

.Onac BP, Mylroie JE, White WB. (2001) Mineralogy of cave deposits on San Salvador Island, Bahamas.

Carbonates and Evaporites ''Carbonates and Evaporites'' is an international scientific journal published 4 times a year by Springer and provides a forum for the exchange of concepts, research, and applications on all aspects of carbonate and evaporite geology. This include ...

, 16, 8-16.Onac BP., Verdes DS. (2003) Sequence of secondary phosphates deposition in a karst environment: evidence from Măgurici Cave (Romania). European Journal of Mineralogy, 15, 741-745. It has been presumed that in sequence hydroxylapatite is deposited followed by the formation of cesanite when the solution in which the crystals are being formed is rich in sodium and sulfate and depleted of calcium.

References

External links