Apatite
Encyclopedia
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
− ion
s, respectively, in the crystal
. The formula of the admixture of the four most common endmembers
is written as Ca
10(PO4
)6(OH,F,Cl,Br)2, and the crystal unit cell formulae of the individual mineral
s are written as Ca10(PO4)6(OH)2, Ca10(PO4)6(F)2, Ca10(PO4)6(Cl)2 and Ca10(PO4)6(Br)2.
Apatite is one of a few minerals that are produced and used by biological micro-environmental systems. Apatite is the defining mineral for 5 on the Mohs scale
. Hydroxyapatite, also known as hydroxylapatite, is the major component of tooth enamel
and bone mineral
. A relatively rare form of apatite in which most of the OH groups are absent and containing many carbonate and acid phosphate substitutions is a large component of bone
material.
Fluorapatite (or fluoroapatite) is more resistant to acid attack than is hydroxyapatite. For this reason, toothpaste typically contains a source of fluoride anions (e.g. sodium fluoride, sodium monofluorophosphate
). Similarly, fluoridated water allows exchange in the teeth
of fluoride ions for hydroxyl groups in apatite. Too much fluoride results in dental fluorosis
and/or skeletal fluorosis
.
Fission tracks
in apatite are commonly used to determine the thermal history of orogenic (mountain) belts and of sediments in sedimentary basin
s. (U-Th)/He dating
of apatite is also well established for use in determining thermal histories and other, less typical applications such as paleo-wildfire dating.
Phosphorite
is a phosphate-rich sedimentary rock
, that contains between 18% and 40% P2O5. The apatite in phosphorite is present as cryptocrystalline
masses referred to as collophane.
During digestion of apatite with sulfuric acid to make phosphoric acid, hydrogen fluoride
is produced as a byproduct from any fluorapatite
content. This byproduct is a minor industrial source of hydrofluoric acid
.
Fluoro-chloro apatite forms the basis of the now obsolete Halophosphor fluorescent tube phosphor system. Dopant elements of manganese and antimony, at less than one mole-percent, in place of the calcium and phosphorus impart the fluorescence, and adjustment of the fluorine to chlorine ratio adjusts the shade of white produced. Now almost entirely replaced by the Tri-Phosphor system.
In the United States
, apatite derived fertilizers are used to supplement the nutrition of many agricultural crops by providing a valuable source of phosphate
.
. Transparent stones of clean color have been faceted, and chatoyant specimens have been cabochon
cut. Chatoyant stones are known as cat's-eye apatite, transparent green stones are known as asparagus stone, and blue stones have been called moroxite
. Crystals of rutile may have grown in the crystal of apatite so when in the right light, the cut stone displays a cat's eye effect. Major sources for gem apatite are Brazil
, Burma, and Mexico
. Other sources include Canada
, Czechoslovakia
, Germany
, India
, Madagascar
, Mozambique
, Norway
, South Africa
, Spain
, Sri Lanka
, and the United States
.
Except some apatite in Florida used to produce phosphate for U.S. tobacco crops contains uranium, radium, lead 210 and polonium 210 and radon.
Apatite is an ore mineral at the Hoidas Lake
rare earth project.
, leading to estimates of water on the lunar surface at a rate of at least 64 parts per billion – 100 times greater than previous estimates – and as high as 5 parts per million. If the minimum amount of mineral-locked water was hypothetically converted to liquid, it would cover the Moon's surface in roughly one meter of water.
Phosphate minerals
Phosphate minerals are those minerals that contain the tetrahedrally coordinated phosphate anion along with the freely substituting arsenate and vanadate...
, usually referring to 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...
, fluorapatite
Fluorapatite
Fluorapatite, often with the alternate spelling of fluoroapatite, is a mineral with the formula Ca53F . Fluorapatite is a hard crystalline solid. Although samples can have various color , the pure mineral is colorless as expected for a material lacking transition metals...
, chlorapatite and bromapatite, named for high concentrations of OH
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...
−, F
Fluoride
Fluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are...
−, Cl
Chloride
The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
− or Br
Bromide
A bromide is a chemical compound containing bromide ion, that is bromine atom with effective charge of −1. The class name can include ionic compounds such as caesium bromide or covalent compounds such as sulfur dibromide.-Natural occurrence:...
− ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
s, respectively, in the 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...
. The formula of the admixture of the four most common endmembers
Endmember (mineralogy)
An endmember in mineralogy is a mineral that is at the extreme end of a mineral series in terms of purity. Minerals often can be described as solid solutions with varying compositions of some chemical elements, rather than as substances with an exact chemical formula...
is written as Ca
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...
10(PO4
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...
)6(OH,F,Cl,Br)2, and the crystal unit cell formulae of the individual mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
s are written as Ca10(PO4)6(OH)2, Ca10(PO4)6(F)2, Ca10(PO4)6(Cl)2 and Ca10(PO4)6(Br)2.
Apatite is one of a few minerals that are produced and used by biological micro-environmental systems. Apatite is the defining mineral for 5 on the Mohs scale
Mohs scale of mineral hardness
The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German geologist and mineralogist Friedrich Mohs and is one of several definitions of hardness in...
. Hydroxyapatite, also known as hydroxylapatite, is the major component of tooth enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...
and bone mineral
Bone mineral
Bone mineral is the inorganic component of bone. Bone mineral is formed from carbonated hydroxyapatite with lower crystallinity....
. A relatively rare form of apatite in which most of the OH groups are absent and containing many carbonate and acid phosphate substitutions is a large component of bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
material.
Fluorapatite (or fluoroapatite) is more resistant to acid attack than is hydroxyapatite. For this reason, toothpaste typically contains a source of fluoride anions (e.g. sodium fluoride, sodium monofluorophosphate
Sodium monofluorophosphate
Sodium monofluorophosphate, commonly abbreviated MFP, is the inorganic compound with the formula Na2PO3F. Typical for a salt, MFP is odourless, colourless, and water-soluble. This salt is an ingredient in some toothpastes.-Uses of MFP:...
). Similarly, fluoridated water allows exchange in the teeth
Tooth
Teeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...
of fluoride ions for hydroxyl groups in apatite. Too much fluoride results in dental fluorosis
Dental fluorosis
Dental fluorosis is a developmental disturbance of dental enamel caused by excessive exposure to high concentrations of fluoride during tooth development. The risk of fluoride overexposure occurs between the ages of 3 months and 8 years. In its mild forms , fluorosis often appears as unnoticeable,...
and/or skeletal fluorosis
Skeletal fluorosis
Skeletal fluorosis is a bone disease caused by excessive consumption of fluoride. In advanced cases, skeletal fluorosis causes pain and damage to bones and joints.-Forms:...
.
Fission tracks
Fission track dating
Fission track dating is a radiometric dating technique based on analyses of the damage trails, or tracks, left by fission fragments in certain uranium-bearing minerals and glasses...
in apatite are commonly used to determine the thermal history of orogenic (mountain) belts and of sediments in sedimentary basin
Sedimentary basin
The term sedimentary basin is used to refer to any geographical feature exhibiting subsidence and consequent infilling by sedimentation. As the sediments are buried, they are subjected to increasing pressure and begin the process of lithification...
s. (U-Th)/He dating
Helium dating
Helium dating may refer to the traditional uranium-thorium dating or uranium-thorium/helium dating.A relatively new dating method, tritium-helium dating has been developed for determining rates of oxygen utilization in the ocean....
of apatite is also well established for use in determining thermal histories and other, less typical applications such as paleo-wildfire dating.
Phosphorite
Phosphorite
Phosphorite, phosphate rock or rock phosphate is a non-detrital sedimentary rock which contains high amounts of phosphate bearing minerals. The phosphate content of phosphorite is at least 15 to 20% which is a large enrichment over the typical sedimentary rock content of less than 0.2%...
is a phosphate-rich sedimentary rock
Sedimentary rock
Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....
, that contains between 18% and 40% P2O5. The apatite in phosphorite is present as cryptocrystalline
Cryptocrystalline
Cryptocrystalline is a rock texture made up of such minute crystals that its crystalline nature is only vaguely revealed even microscopically in thin section by transmitted polarized light. Among the sedimentary rocks, chert and flint are cryptocrystalline. Carbonado, a form of diamond, is also...
masses referred to as collophane.
Uses
The primary use of apatite is in the manufacture of fertilizer – it is a source of phosphorus. It is occasionally used as a gemstone.During digestion of apatite with sulfuric acid to make phosphoric acid, hydrogen fluoride
Hydrogen fluoride
Hydrogen fluoride is a chemical compound with the formula HF. This colorless gas is the principal industrial source of fluorine, often in the aqueous form as hydrofluoric acid, and thus is the precursor to many important compounds including pharmaceuticals and polymers . HF is widely used in the...
is produced as a byproduct from any fluorapatite
Fluorapatite
Fluorapatite, often with the alternate spelling of fluoroapatite, is a mineral with the formula Ca53F . Fluorapatite is a hard crystalline solid. Although samples can have various color , the pure mineral is colorless as expected for a material lacking transition metals...
content. This byproduct is a minor industrial source of hydrofluoric acid
Hydrofluoric acid
Hydrofluoric acid is a solution of hydrogen fluoride in water. It is a valued source of fluorine and is the precursor to numerous pharmaceuticals such as fluoxetine and diverse materials such as PTFE ....
.
Fluoro-chloro apatite forms the basis of the now obsolete Halophosphor fluorescent tube phosphor system. Dopant elements of manganese and antimony, at less than one mole-percent, in place of the calcium and phosphorus impart the fluorescence, and adjustment of the fluorine to chlorine ratio adjusts the shade of white produced. Now almost entirely replaced by the Tri-Phosphor system.
In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, apatite derived fertilizers are used to supplement the nutrition of many agricultural crops by providing a valuable source of 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...
.
Gemology
Apatite is infrequently used as a gemstoneGemstone
A gemstone or gem is a piece of mineral, which, in cut and polished form, is used to make jewelry or other adornments...
. Transparent stones of clean color have been faceted, and chatoyant specimens have been cabochon
Cabochon
A cabochon , from the Middle French caboche , is a gemstone which has been shaped and polished as opposed to faceted. The resulting form is usually a convex top with a flat bottom. Cutting en cabochon is usually applied to opaque gems, while faceting is usually applied to transparent stones...
cut. Chatoyant stones are known as cat's-eye apatite, transparent green stones are known as asparagus stone, and blue stones have been called moroxite
Moroxite
Moroxite is a mineral, a crystallized form of apatite. It has a greenish-blue or brown color. It is found in Aren-dal, Norway, and also in Pargas, Finland. The name is derived from a certain Greek word applied to a stone used by the Ancients in bleaching linen....
. Crystals of rutile may have grown in the crystal of apatite so when in the right light, the cut stone displays a cat's eye effect. Major sources for gem apatite are Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
, Burma, and Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. Other sources include Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, Czechoslovakia
Czechoslovakia
Czechoslovakia or Czecho-Slovakia was a sovereign state in Central Europe which existed from October 1918, when it declared its independence from the Austro-Hungarian Empire, until 1992...
, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
, Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...
, Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
, South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
, Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...
, and the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
.
Use as an ore mineral
Apatite is occasionally found to contain significant amounts of rare earth elements and can be used as an ore for those metals. This is preferable to traditional rare earth ores, as apatite is non-radioactive and does not pose an environmental hazard in mine tailings.Except some apatite in Florida used to produce phosphate for U.S. tobacco crops contains uranium, radium, lead 210 and polonium 210 and radon.
Apatite is an ore mineral at the Hoidas Lake
Hoidas Lake
Hoidas Lake is a remote northern Canadian lake which lies approximately 50 kilometers north of Uranium City, Saskatchewan. Named in honor of Irvin Frank Hoidas, a Royal Canadian Air Force pilot officer killed in action during the Second World War when his Stirling W-7520 crashed near the Belgian...
rare earth project.
Thermodynamics
The standard (p = 0.1 MPa) molar enthalpies of formation in the crystalline state of hydroxyapatite, chlorapatite and a preliminary value for bromapatite, at T = 298.15 K, have already been determined by reaction-solution calorimetry. Speculations on the existence of a possible fifth member of the calcium apatites family, iodoapatite, have been drawn from energetic considerations.Lunar science
Moon rocks collected by astronauts during the Apollo program contain traces of apatite. Re-analysis of these samples in 2010 revealed water trapped in the mineral as hydroxylHydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...
, leading to estimates of water on the lunar surface at a rate of at least 64 parts per billion – 100 times greater than previous estimates – and as high as 5 parts per million. If the minimum amount of mineral-locked water was hypothetically converted to liquid, it would cover the Moon's surface in roughly one meter of water.
See also
- List of minerals
- Thermal history modellingThermal history modellingThermal history modelling is an exercise undertaken during basin modelling to evaluate the temperature history of stratigraphic layers in a sedimentary basin....
- Hexafluorosilicic acid
Further reading
- Schmittner Karl-Erich and Giresse Pierre, 1999. Micro-environmental controls on biomineralization: superficial processes of apatite and calcite precipitation in Quaternary soils, Roussillon, France. Sedimentology 46/3: 463–476.