# Cesanite
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{{Infobox mineral
| name = Cesanite
| category = [Sulfate minerals](/source/Sulfate_minerals)
| boxwidth =
| boxbgcolor =
| image = Cesanite.jpg
| imagesize =
| caption =
| formula = Ca2Na3[(OH)(SO4)3]
| IMAsymbol=Csa[{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}]
| molweight =
| strunz = 7.BD.20
| system = [Hexagonal](/source/Hexagonal_crystal_system)
| class = Trigonal dipyramidal ({{overline|3}}m)
[H-M symbol](/source/H-M_symbol): ({{overline|6}})
| symmetry = ''P''{{overline|6}}
| unit cell = a = 9.44 Å, c = 6.9 Å; Z = 1
| color = Colorless to white
| habit = Massive granular, rarely as striated subhedral prismatic crystals
| twinning = On {10{{overline|1}}0}
| cleavage = On {0001}
| fracture =
| tenacity =
| mohs = 2-3
| luster = Greasy to silky in aggregates
| polish =
| refractive = nω = 1.570 nε = 1.564
| opticalprop = Uniaxial (-)
| birefringence =
| dispersion =
| pleochroism =
| fluorescence=
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| streak =
| gravity = 2.96-3.02
| density =
| fusibility =
| diagnostic =
| solubility = Slight in water
| diaphaneity = Transparent to translucent
| other =
| references = [[https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Cesanite Mineralienatlas]][Cavarretta G., Mottana A., Tecce F. (1981) Cesanite, Ca2Na3[(OH)(SO4)3], a sulfate isotypic to apatite, from the Cesano Geothermal-Field (Lathium, Italy). Mineralogical Magazine, 44, 269-273.][Piotrowski A., Kahlenberg V., Fischer RX., etal. (2002) The crystal structures of cesanite and its synthetic analogue – A comparison. American Mineralogist, 87, 715-720.][[https://www.handbookofmineralogy.org/pdfs/cesanite.pdf Handbook of Mineralogy]][[http://www.mindat.org/min-938.html Mindat.org]][[https://webmineral.com/data/Cesanite.shtml Webmineral data]]
}}
'''Cesanite''' is the end member of the [apatite](/source/apatite)-[wilkeite](/source/wilkeite)-[ellestadite](/source/ellestadite) series that substitutes all of apatite's [phosphate](/source/phosphate) [ions](/source/ions) with [sulfate](/source/sulfate) ions and balances the difference in charge by replacing several [calcium](/source/calcium) ions with [sodium](/source/sodium) ions. Currently very few sites bearing cesanite have been found and are limited to a geothermal field in [Cesano](/source/Cesano_(RM)), [Italy](/source/Italy) from which its name is derived, [Măgurici Cave](/source/M%C4%83gurici_Cave) in [Romania](/source/Romania), and in the [San Salvador Island](/source/San_Salvador_Island) [cave](/source/cave)s in the [Bahamas](/source/Bahamas).
==History==
Cesanite was first discovered in 1981 while the [Italian National Electricity Board](/source/Italian_National_Electricity_Board) was doing [exploratory drilling](/source/exploratory_drilling) to examine a reservoir of heated [brine](/source/brine) to determine its potential as a [geothermal energy](/source/geothermal_energy) source. When it was first found it was thought to be an apatite until after more thorough examination.[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](/source/space_group) ''P''{{overline|6}}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](/source/Structural_analog). After this study it was found that the [crystal structure](/source/crystal_structure) of cesanite to be [isostructural](/source/isostructural) to this [synthetic](/source/Chemical_synthesis) 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''{{overline|6}}. It can be inferred that the reason the mistake went unnoticed for so long is that cesanite retains [pseudo-symmetry](/source/pseudo-symmetry) in the array of its tetrahedra that closely mimics ''P''{{overline|6}}3/m.[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](/source/fracture) sealing process where cesanite [crystal](/source/crystal)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](/source/g%C3%B6rgeyite) crystals.[Onac BP, Mylroie JE, White WB. (2001) Mineralogy of cave deposits on San Salvador Island, Bahamas. [Carbonates and Evaporites](/source/Carbonates_and_Evaporites), 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.