Apatite

Apatite group
Apatite group
	Apatite (CaF) (fluorapatite) doubly-terminated crystal in calcite
General
Category	Phosphate mineral
Formula; (repeating unit)	Ca5(PO4)3(F,Cl,OH)
IMA symbol	Ap
Strunz classification	8.BN.05
Crystal system	Hexagonal
Crystal class	Dipyramidal (6/m) ; (same H-M symbol)
Space group	P63/m (no. 176)
Identification
Color	Transparent to translucent, usually green, less often colorless, yellow, blue to violet, pink, brown.
Crystal habit	Tabular, prismatic crystals, massive, compact or granular
Cleavage	[0001] indistinct, [1010] indistinct
Fracture	Conchoidal to uneven
Mohs scale hardness	5 (defining mineral)
Luster	Vitreous to subresinous
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity	3.16–3.22
Polish luster	Vitreous
Optical properties	Double refractive, uniaxial negative
Refractive index	1.634–1.638 (+0.012, −0.006)
Birefringence	0.002–0.008
Pleochroism	Blue stones – strong, blue and yellow to colorless. Other colors are weak to very weak.
Dispersion	0.013
Ultraviolet fluorescence	Yellow stones – purplish-pink, which is stronger in long wave; blue stones – blue to light-blue in both long and short wave; green stones – greenish-yellow, which is stronger in long wave; violet stones – greenish-yellow in long wave, light-purple in short wave.

Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH⁻, F⁻ and Cl⁻ ion, respectively, in the crystal. The formula of the admixture of the three most common endmembers is written as Ca₁₀(PO₄)₆(OH,F,Cl)₂, and the crystal unit cell formulae of the individual minerals are written as Ca₁₀(PO₄)₆(OH)₂, Ca₁₀(PO₄)₆F₂ and Ca₁₀(PO₄)₆Cl₂.

The mineral was named apatite by the German geologist Abraham Gottlob Werner in 1786,^[4] although the specific mineral he had described was reclassified as fluorapatite in 1860 by the German mineralogist Karl Friedrich August Rammelsberg. Apatite is often mistaken for other minerals. This tendency is reflected in the mineral's name, which is derived from the Greek word ἀπατάω (apatáō), which means to deceive.^[5]^[6]

^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
^ ^a ^b ^c ^d Apatite. Webmineral
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k Gemological Institute of America, GIA Gem Reference Guide 1995, ISBN 0-87311-019-6
^
According to Werner himself – (Werner, 1788), p. 85 – the name "apatite" first appeared in print in:
- Gerhard, C.A., Grundriss des Mineral-systems [Outline of the system of minerals] (Berlin, (Germany): Christian Friedrich Himburg, 1786), p. 281. From p. 281: "Von einigen noch nicht genau bestimmten und ganz neu entdeckten Mineralien. Ich rechne hierzu folgende drei Körper: 1. Den Apatit des Herrn Werners. … "(On some still not precisely determined and quite recently discovered minerals. I count among these the following three substances: 1. the apatite of Mr. Werner. … )
Werner described the mineral in some detail in an article of 1788.
- Werner, A.G. (1788) "Geschichte, Karakteristik, und kurze chemische Untersuchung des Apatits" (History, characteristics, and brief chemical investigation of apatite), Bergmännisches Journal (Miners' Journal), vol. 1, pp. 76–96. On pp. 84–85, Werner explained that because mineralogists had repeatedly misclassified it (e.g., as aquamarine), he gave apatite the name of "deceiver": "Ich wies hierauf diesem Foßile, als einer eigenen Gattung, sogleich eine Stelle in dem Kalkgeschlechte an; und ertheilte ihm, – weil es bisher alle Mineralogen in seiner Bestimmung irre geführt hatte, – den Namen Apatit, den ich von dem griechischen Worte απατάω (decipio) bildete, und welcher so viel as Trügling sagt." (I then immediately assigned to this fossil [i.e., material obtained from underground], as a separate type, a place in the lime lineage; and conferred on it – because it had previously led astray all mineralogists in its classification – the name "apatite", which I formed from the Greek word απατάω [apatáō] (I deceive) and which says as much as [the word] "deceiver".)
^ "ἀπατάω". Logeion. Archived from the original on Feb 22, 2023. Retrieved Feb 22, 2023.
^ "Fluorapatite mineral information and data". mindat.org. Retrieved 30 January 2018.

[1] Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.

[Webmineral-2] Apatite. Webmineral

[GRG-3] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k Gemological Institute of America, GIA Gem Reference Guide 1995, ISBN 0-87311-019-6

[4] According to Werner himself – (Werner, 1788), p. 85 – the name "apatite" first appeared in print in:
Gerhard, C.A., Grundriss des Mineral-systems [Outline of the system of minerals] (Berlin, (Germany): Christian Friedrich Himburg, 1786), p. 281. From p. 281: "Von einigen noch nicht genau bestimmten und ganz neu entdeckten Mineralien. Ich rechne hierzu folgende drei Körper: 1. Den Apatit des Herrn Werners. … "(On some still not precisely determined and quite recently discovered minerals. I count among these the following three substances: 1. the apatite of Mr. Werner. … )
Werner described the mineral in some detail in an article of 1788.
Werner, A.G. (1788) "Geschichte, Karakteristik, und kurze chemische Untersuchung des Apatits" (History, characteristics, and brief chemical investigation of apatite), Bergmännisches Journal (Miners' Journal), vol. 1, pp. 76–96. On pp. 84–85, Werner explained that because mineralogists had repeatedly misclassified it (e.g., as aquamarine), he gave apatite the name of "deceiver": "Ich wies hierauf diesem Foßile, als einer eigenen Gattung, sogleich eine Stelle in dem Kalkgeschlechte an; und ertheilte ihm, – weil es bisher alle Mineralogen in seiner Bestimmung irre geführt hatte, – den Namen Apatit, den ich von dem griechischen Worte απατάω (decipio) bildete, und welcher so viel as Trügling sagt." (I then immediately assigned to this fossil [i.e., material obtained from underground], as a separate type, a place in the lime lineage; and conferred on it – because it had previously led astray all mineralogists in its classification – the name "apatite", which I formed from the Greek word απατάω [apatáō] (I deceive) and which says as much as [the word] "deceiver".)

[5] Gerhard, C.A., Grundriss des Mineral-systems [Outline of the system of minerals] (Berlin, (Germany): Christian Friedrich Himburg, 1786), p. 281. From p. 281: "Von einigen noch nicht genau bestimmten und ganz neu entdeckten Mineralien. Ich rechne hierzu folgende drei Körper: 1. Den Apatit des Herrn Werners. … "(On some still not precisely determined and quite recently discovered minerals. I count among these the following three substances: 1. the apatite of Mr. Werner. … )

[6] Werner, A.G. (1788) "Geschichte, Karakteristik, und kurze chemische Untersuchung des Apatits" (History, characteristics, and brief chemical investigation of apatite), Bergmännisches Journal (Miners' Journal), vol. 1, pp. 76–96. On pp. 84–85, Werner explained that because mineralogists had repeatedly misclassified it (e.g., as aquamarine), he gave apatite the name of "deceiver": "Ich wies hierauf diesem Foßile, als einer eigenen Gattung, sogleich eine Stelle in dem Kalkgeschlechte an; und ertheilte ihm, – weil es bisher alle Mineralogen in seiner Bestimmung irre geführt hatte, – den Namen Apatit, den ich von dem griechischen Worte απατάω (decipio) bildete, und welcher so viel as Trügling sagt." (I then immediately assigned to this fossil [i.e., material obtained from underground], as a separate type, a place in the lime lineage; and conferred on it – because it had previously led astray all mineralogists in its classification – the name "apatite", which I formed from the Greek word απατάω [apatáō] (I deceive) and which says as much as [the word] "deceiver".)

[5] "ἀπατάω". Logeion. Archived from the original on Feb 22, 2023. Retrieved Feb 22, 2023.

[6] "Fluorapatite mineral information and data". mindat.org. Retrieved 30 January 2018.

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