Cesanite
Encyclopedia
Cesanite is the end member of the apatite
-wilkeite-ellestadite series that substitutes all of apatite's phosphate
ions with sulfate
ions and balances the difference in charge by replacing several calcium
ions with sodium
ions. Currently very few sites bearing cesanite have been found and are limited to a geothermal field in Cesano
, Italy
from which its name is derived, Măgurici Cave in Romania
, and in the San Salvador Island
cave
s in the Bahamas.
to determine its potential as a geothermal energy source. When it was first found it was thought to be an apatite until after more thorough examination.
. This was determined by refining the original unit cell dimensions and comparing them to the atomic coordinates of Holly Springs hydroxylapatite. From this it was extrapolated that although different element
s are substituted for cesanite, the structure and cell parameters are nearly the same with some differences in the bond length
s of the tetrahedras. This similarity was to confirm the space group
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. After this study it was found that the crystal structure
of cesanite to be infrastructural to this synthetic
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 . 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 3/m.
Cesanite's crystal structure is made up of tetrahedra of sulfide
cations surrounded by oxygen
anions distributed along with hydroxide
ions around the Ca and Na ions occupying the M1 through four sites. The M1 and M2 cites create distorted pentagonal bipyramids while the M3 and M4 create tricapped trigonal prisms
. The M3 and M4 polyhedra share faces when they are next to each other and form columns parallel to [001] while isolated sulfate tetrahedra alternate along the c axis.
. 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.
sealing process where cesanite 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 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 gypsum
and in 2003 inside Măgurici Cave in Romania it was found in close association with hydroxylapatite
. 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.
Apatite
Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH−, F−, Cl− or Br− ions, respectively, in the crystal...
-wilkeite-ellestadite series that substitutes all of apatite's phosphate
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...
ions with sulfate
Sulfate
In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
ions and balances the difference in charge by replacing several calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
ions with sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
ions. Currently very few sites bearing cesanite have been found and are limited to a geothermal field in Cesano
Cesano (RM)
Cesano is a frazione of the comune of Rome, Italy. It is a small medieval burgh on the Via Cassia, located in the municipality's Municipio XX, 27 km from Rome proper....
, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
from which its name is derived, Măgurici Cave in Romania
Romania
Romania is a country located at the crossroads of Central and Southeastern Europe, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea...
, and in the San Salvador Island
San Salvador Island
San Salvador Island, also known as Watlings Island, is an island and district of the Bahamas. Until 1986, when the National Geographic Society suggested Samana Cay, it was widely believed that during his first expedition to the New World, San Salvador Island was the first land sighted and visited...
cave
Cave
A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...
s in the Bahamas.
History
Cesanite was first discovered in 1981 while the Italian National Electricity Board was doing exploratory drilling to examine a reservoir of heated brineBrine
Brine is water, saturated or nearly saturated with salt .Brine is used to preserve vegetables, fruit, fish, and meat, in a process known as brining . Brine is also commonly used to age Halloumi and Feta cheeses, or for pickling foodstuffs, as a means of preserving them...
to determine its potential as a geothermal energy 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 hydroxylapatiteHydroxylapatite
Hydroxylapatite, also called hydroxyapatite , is a naturally occurring mineral form of calcium apatite with the formula Ca53, but is usually written Ca1062 to denote that the crystal unit cell comprises two entities. Hydroxylapatite is the hydroxyl endmember of the complex apatite group...
. This was determined by refining the original unit cell dimensions and comparing them to the atomic coordinates of Holly Springs hydroxylapatite. From this it was extrapolated that although different element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
s are substituted for cesanite, the structure and cell parameters are nearly the same with some differences in the bond length
Bond length
- Explanation :Bond length is related to bond order, when more electrons participate in bond formation the bond will get shorter. Bond length is also inversely related to bond strength and the bond dissociation energy, as a stronger bond will be shorter...
s of the tetrahedras. This similarity was to confirm the space group
Space group
In mathematics and geometry, a space group is a symmetry group, usually for three dimensions, that divides space into discrete repeatable domains.In three dimensions, there are 219 unique types, or counted as 230 if chiral copies are considered distinct...
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. After this study it was found that the crystal structure
Crystal structure
In mineralogy and crystallography, crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid. A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long-range order and symmetry...
of cesanite to be infrastructural to this synthetic
Chemical synthesis
In chemistry, chemical synthesis is purposeful execution of chemical reactions to get a product, or several products. This happens by physical and chemical manipulations usually involving one or more reactions...
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 . 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 3/m.
Cesanite's crystal structure is made up of tetrahedra of sulfide
Sulfide
A sulfide is an anion of sulfur in its lowest oxidation state of 2-. Sulfide is also a slightly archaic term for thioethers, a common type of organosulfur compound that are well known for their bad odors.- Properties :...
cations surrounded by oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
anions distributed along with hydroxide
Hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and a hydrogen atom held together by a covalent bond, and carrying a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, as a ligand, a nucleophile, and a...
ions around the Ca and Na ions occupying the M1 through four sites. The M1 and M2 cites create distorted pentagonal bipyramids while the M3 and M4 create tricapped trigonal prisms
Prism (geometry)
In geometry, a prism is a polyhedron with an n-sided polygonal base, a translated copy , and n other faces joining corresponding sides of the two bases. All cross-sections parallel to the base faces are the same. Prisms are named for their base, so a prism with a pentagonal base is called a...
. The M3 and M4 polyhedra share faces when they are next to each other and form columns parallel to [001] while 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 an other pyramid. According to the newest sources the cells spacings for cesanite are 9.4630 along its a-axises and 6.9088 along its c-axis. In thin section cesanite remains transparent and has moderate birefringenceBirefringence
Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certain anisotropic materials, such as crystals of calcite or boron nitride. The effect was first described by the Danish scientist Rasmus Bartholin in 1669, who saw it in calcite...
. 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.
Geologic occurrence
Cesanite has been found in only three places to date. The original occurrence was observed as part of a fractureFracture
A fracture is the separation of an object or material into two, or more, pieces under the action of stress.The word fracture is often applied to bones of living creatures , or to crystals or crystalline materials, such as gemstones or metal...
sealing process where cesanite crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
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 gypsum
Gypsum
Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...
and in 2003 inside Măgurici Cave in Romania it was found in close association with hydroxylapatite
Hydroxylapatite
Hydroxylapatite, also called hydroxyapatite , is a naturally occurring mineral form of calcium apatite with the formula Ca53, but is usually written Ca1062 to denote that the crystal unit cell comprises two entities. Hydroxylapatite is the hydroxyl endmember of the complex apatite group...
. 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.