**1.1. Nomenclature of apatite minerals and apatite supergroup**

The mineral apatite was first recognized by German geologist ABRAHAM GOTTLOB WERNER (1950– 1817) and named in 1786 from Greek word "*apatao*" (απα'ταω, which means to mislead, to cheat, or to deceive because the mineral was often mistaken for other species, e.g. mineral beryl (Be3Al2Si6O18, space group P6/MCC)) [43],[44],[45],[46].

<sup>14</sup> There are 14 Bravais lattices, 32 point groups (crystal classes), and 230 crystallographic space groups in three dimensions [28]. The space groups were independently described by E.S. FEDEROV (1853–1919, Russian), A.M. SCHÖNFLIES (1853–1928, German), and W. BARLOW (1845–1934, English) [32].

<sup>15</sup> The corresponding Schönflies symbol is C6h2 . The number of group is 176.

<sup>16</sup> Hexad denotes the sixfold rotation axis. The 4-, 3-, 2-, and 1-fold rotation axes are termed as tetrad, triad, diad, and monad [27].

<sup>17</sup> Glide plane combines a reflection with a translation parallel to the plane.

Since 1856–1860, these minerals have been named fluorapatite, chlorapatite, and hydroxyla‐ patite, depending on the dominant *Z*<sup>−</sup> anion. The increasing number of new discovered species18 resulted in a revision of the mineralogical nomenclature, which was initiated by the chair‐ man of the IMA Commission on New Minerals, Nomenclature and Classification, E.A.J. BURKE, and aimed at adopting, as far as possible, modified Levinson suffixes19 (or Levinson modifier [47],[49]) instead of adjectival prefixes such as fluor-, chlor- and hydroxyl. The above-men‐ tioned minerals were renamed to apatite–(CaF), apatite–(CaCl) and apatite–(CaOH).20

One of the rationales for that change was the benefit of having the names of these minerals appear consecutively in alphabetical listings and databases. These changes did not fully consider the structural complexity of minerals with the apatite structure [45],[49],[50]. The name of these minerals was currently changed back from apatite–CaF) apatite–(CaOH), apatite–(CaCl) to fluorapatite, hydroxylapatite and chlorapatite. Furthermore, the monoclin‐ ic variants21 [51] fluorapatite—M, hydroxylapatite—M and chlorapatite—M are not consid‐ ered to be distinct species [45].

The recently approved nomenclature scheme [49] could logically be extended to other minerals from the group of apatite, e.g. pyromorphite [52] should be named as apatite–(PbCl) or alforsite [53],[54] as apatite–(BaCl). It is also possible to include various tetrahedral cations (P, As, or V) into the extended suffix, e.g. apatite–(PbAsCl) instead of mimetite [55]. The results would be the mineral names, which are more similar to chemical formula [45]. The name mimetite–M is used for the polymorphic variant of mimetite. The mineral was previously known as clinomimetite and currently is not considered a distinct species [45].

The "apatite group" traditionally includes phosphate, arsenate and vanadate minerals. Other minerals belonging to different chemical classes, namely, silicates (e.g. britholite–(Ce) [56],[57] or britholite–(Y) [57],[58]), silicate-sulfates (e.g. hydroxylellestadite [45],[59], fluorellestadite [45],[60] and chlorellestadite22 [45]) and sulfates (e.g. cesanite [61]) display the structural

<sup>18</sup> The concept of mineral species is defined mainly on the basis of its chemical composition and crystallographic properties. For example, hydroxylapatite and fluorapatite both crystallize in the hexagonal system, with the same space group and have similar unit-cell parameters. They are considered as the separate species because the relevant structural site is predominantly occupied by OH<sup>−</sup> in hydroxylapatite and by F<sup>−</sup> in fluorapatite [4].

<sup>19</sup> The nomenclature system based on chemical-symbol suffixes described by LEVISON [47] and originally applied only to rare-earth mineral species, which are defined to have the total atomic percentage of rare-earth elements and Y greater than any other element within a single set of crystal-structure sites, e.g. (~REE, Ca). A species name is related to a rareearth mineral whenever the presence of rare-earth element distribution is determined. The chemical symbol for the predominant rare-earth element is appended, in parentheses, by means of a hyphen to the group name; this results in mineral species names such as monazite-(Ce), monazite-(La), and monazite-(Nd) [48]. If a rare-earth mineral appears together with considerable quantities of another rare-earth element which is unusual, or for any reason deserving the notice, two or more chemical symbols may be placed in the parentheses [47]. For example, a monazite–(Ce) with a considerable amount of samarium would be written as monazite–(Ce,Sm).

<sup>20</sup> Another examples are strontium apatite named as apatite-(SrOH) and clinohydroxylapatite named as apatite–(CaOH)– M.

<sup>21</sup> In essence, the polytypes are distinguished by alphanumerical symbols appended to the root name and joined to by a hyphen, for example, wollastonite-3*T* or graphite-2*H*. The numerical part of the symbol represents the layering periodicity and the alphabetical part, rendered in italic print represents the crystallographic system as follows: cubic (C), hexagonal (H), rhombohedral (R), trigonal (T), orthorhombic (O), monoclinic (M), and triclinic (A).

<sup>22</sup> The names of ellestadite–(OH), ellestadite–(F), and ellestadite–(Cl) minerals were changed back to hydroxylellestadite, fluorellestadite, and chlorellestadite, respectively [45],[49].

morphology of apatite. In accordance with the newly approved standardization of mineral group hierarchies, all of these minerals can be included in the broader apatite supergroup [45].

Since 1856–1860, these minerals have been named fluorapatite, chlorapatite, and hydroxyla‐

resulted in a revision of the mineralogical nomenclature, which was initiated by the chair‐ man of the IMA Commission on New Minerals, Nomenclature and Classification, E.A.J. BURKE,

[47],[49]) instead of adjectival prefixes such as fluor-, chlor- and hydroxyl. The above-men‐

One of the rationales for that change was the benefit of having the names of these minerals appear consecutively in alphabetical listings and databases. These changes did not fully consider the structural complexity of minerals with the apatite structure [45],[49],[50]. The name of these minerals was currently changed back from apatite–CaF) apatite–(CaOH), apatite–(CaCl) to fluorapatite, hydroxylapatite and chlorapatite. Furthermore, the monoclin‐

The recently approved nomenclature scheme [49] could logically be extended to other minerals from the group of apatite, e.g. pyromorphite [52] should be named as apatite–(PbCl) or alforsite [53],[54] as apatite–(BaCl). It is also possible to include various tetrahedral cations (P, As, or V) into the extended suffix, e.g. apatite–(PbAsCl) instead of mimetite [55]. The results would be the mineral names, which are more similar to chemical formula [45]. The name mimetite–M is used for the polymorphic variant of mimetite. The mineral was previously

The "apatite group" traditionally includes phosphate, arsenate and vanadate minerals. Other minerals belonging to different chemical classes, namely, silicates (e.g. britholite–(Ce) [56],[57] or britholite–(Y) [57],[58]), silicate-sulfates (e.g. hydroxylellestadite [45],[59], fluorellestadite

18 The concept of mineral species is defined mainly on the basis of its chemical composition and crystallographic properties. For example, hydroxylapatite and fluorapatite both crystallize in the hexagonal system, with the same space group and have similar unit-cell parameters. They are considered as the separate species because the relevant structural

19 The nomenclature system based on chemical-symbol suffixes described by LEVISON [47] and originally applied only to rare-earth mineral species, which are defined to have the total atomic percentage of rare-earth elements and Y greater than any other element within a single set of crystal-structure sites, e.g. (~REE, Ca). A species name is related to a rareearth mineral whenever the presence of rare-earth element distribution is determined. The chemical symbol for the predominant rare-earth element is appended, in parentheses, by means of a hyphen to the group name; this results in mineral species names such as monazite-(Ce), monazite-(La), and monazite-(Nd) [48]. If a rare-earth mineral appears together with considerable quantities of another rare-earth element which is unusual, or for any reason deserving the notice, two or more chemical symbols may be placed in the parentheses [47]. For example, a monazite–(Ce) with a

20 Another examples are strontium apatite named as apatite-(SrOH) and clinohydroxylapatite named as apatite–(CaOH)–

21 In essence, the polytypes are distinguished by alphanumerical symbols appended to the root name and joined to by a hyphen, for example, wollastonite-3*T* or graphite-2*H*. The numerical part of the symbol represents the layering periodicity and the alphabetical part, rendered in italic print represents the crystallographic system as follows: cubic (C), hexagonal

22 The names of ellestadite–(OH), ellestadite–(F), and ellestadite–(Cl) minerals were changed back to hydroxylellestadite,

in hydroxylapatite and by F<sup>−</sup>

considerable amount of samarium would be written as monazite–(Ce,Sm).

fluorellestadite, and chlorellestadite, respectively [45],[49].

(H), rhombohedral (R), trigonal (T), orthorhombic (O), monoclinic (M), and triclinic (A).

[45]) and sulfates (e.g. cesanite [61]) display the structural

in fluorapatite [4].

known as clinomimetite and currently is not considered a distinct species [45].

[51] fluorapatite—M, hydroxylapatite—M and chlorapatite—M are not consid‐

tioned minerals were renamed to apatite–(CaF), apatite–(CaCl) and apatite–(CaOH).20

and aimed at adopting, as far as possible, modified Levinson suffixes19

8 Apatites and their Synthetic Analogues - Synthesis, Structure, Properties and Applications

anion. The increasing number of new discovered species18

(or Levinson modifier

patite, depending on the dominant *Z*<sup>−</sup>

ic variants21

ered to be distinct species [45].

[45],[60] and chlorellestadite22

site is predominantly occupied by OH<sup>−</sup>

M.

The valid IMA-accepted mineral species within the apatite supergroup can be divided into five groups [45]:


All of valid species within the apatite supergroup are listed in **Table 3**. There are also other minerals with the apatite structure [45]:



<sup>23</sup> Melanocerite–Ce and tritomite–(Ce) are probably the same mineral, and tritomite-(Y) could be the Y-dominant analogue [45].



a The suffix –H could be used to denote the hexagonal polymorph.

b The name of monoclinic polymorph that should no longer to be considered as distinct species.

c Mineral approved by the IMA CNMNC without a name.

d Potentially new mineral species.

**Group Existing name (IMA list of minerals) Approved name End-member formula**

Apatite–(CaOH)–*M* Hydroxylapatite–*M*<sup>b</sup>

10 Apatites and their Synthetic Analogues - Synthesis, Structure, Properties and Applications

Fermorite Johnbaumite–*M*<sup>b</sup>

Clinomimetite Mimetite–*M*<sup>b</sup>

Hedyphane group

Apatite–(CaOH) Hydroxylapatitea Ca5(PO4)3OH

Svabite Svabite Ca5(AsO4)3F Turneaureite Turneaureite Ca5(AsO4)3Cl Johnbaumite Johnbaumitea Ca5(AsO4)3OH

2008-009c Stronadelphite Sr5(PO4)3F Pyromorphyte Pyromorphyte Pb5(PO4)3Cl Mimetite Mimetitea Pb5(AsO4)3Cl

Alforsite Alforsite Ba5(PO4)3Cl Vanadinite Vanadinite Pb5(VO4)3Cl

– "**Hydroxylphosphohedy**

Belovite group Fluorcaphite Fluorcaphite SrCaCa3(PO4)3F

Britholite group Britholite–(Ce) Britholite–(Ce) (Ce,Ca)5(SiO4)3OH

Hedyphane Hedyphane Ca2Pb3(AsO4)3Cl – "**Hydroxylhedyphane**"d Ca2Pb3(AsO4)3OH Phosphohedyphane Phosphohedyphane Ca2Pb3(PO4)3Cl Phosphohedyphane–(F) **Fluorphosphohedyphane** Ca2Pb3(PO4)3F

**phane**"d

– **New root name**<sup>d</sup> Ca2Sr3(PO4)3F Morelandite Morelandite **Ca2Ba3(AsO4)3F,Cl** – **New root name**<sup>d</sup> Mn2Ca3(PO4)3Cl Cesanite Cesanite Ca2Na3(SO4)3OH Caracolite Caracolite Na2(Pb2Na)(SO4)3Cl Aiolosite Aiolosite Na2(Na2Bi)(SO4)3Cl

Apatite–(SrOH) **Fluorstrophite** SrCaSr3(PO4)3Fe Deloneite–(Ce) **Deloneite (Na0.5REE0.25Ca0.25)**

Belovite–(Ce) Belovite–(Ce) NaCeSr3(PO4)3F Belovite–(La) Belovite–(La) NaLaSr3(PO4)3F Kuannersuite–(Ce) Kuannersuite–(Ce) NaCeBa3(PO4)3F0.5Cl0.5

Britholite–(Y) Britholite–(Y) (Y,Ca)5(SiO4)3OH

Ca2Pb3(PO4)3OH

**(Ca0.75REE0.25)Sr1.5(CaNa0.25REE0.25)**

**(PO4)3F0.5(OH)0.5**

e A mistake in the IMA list of minerals, please see PASERO et al [45] for further details. Since the mineral was initially considered to be the Sr-dominant analogue of fluorapatite with simplified formula (Sr,Ca)5(PO4)3(F,OH), it was named as strontium apatite. Later structural study determined the idealized formula of mineral as SrCaSr3(PO4)3F. Recently, the mineral was renamed as apatite–(SrOH) [45],[49]. However, the name should have been changed to apatite–(SrF) given that fluorine is the dominant Z<sup>−</sup> anion.

f Mineral to be potentially discredited (= tritomite–(Ce)).

g Mineral be discredited (a mineral with ideal end-member formula Ca5(SiO4)1.5(SO4)1.5Cl is assumed not to exist).

**Table 3.** Existing (IMA) approved names and end-member formulas for the minerals within the apatite supergroup. Approved changes are marked by bold and names in quotes are the most appropriate for potential new minerals.

The nomenclature of minerals from the apatite group is very confusing because many of the names are initially used to ill-defined varieties, which did not deserve specific status. There are many historical names,24 which still appear in literature [10],[67],[68]:


<sup>24</sup> These names are no longer accepted by IMA/CNMMN.

<sup>25</sup> Described deeply in **Section 2.6** and **Chapter 7**.


The most frequent color of foliated apatite is snow-white, yellowish-whiter, reddish-white and greenish-white. Several of these colors occur frequently in the same piece. It sometimes occurs also as massive and disseminated in distinct concretions, which are large and small angulo-granular, and sometimes thin and straight lamellar, generally crystallized. The crystals are small, very small and middle-sized and occur sometimes single, sometimes many irregularly superimposed on each other. It is brittle and easily fragile. Foliated apatite becomes electric by heating and by being rubbed with woolen cloth. On glowing coals, it emits a pale grass-green phosphoric light [79]

**• Conchoidal apatite or asparagus**-**stone**: a yellow-green variety of apatite. The name of asparagus stone has been given to this variety in allusion to asparagus green color, which it frequently exhibits. It was distinguished from the apatite partly by its crystalline form, and more particularly by tendency to phosphoresce on hot coals. It presents either the primitive or the perfect form, or it occurs with truncated lateral edges, but most frequent‐ ly, the hexahedral prism is terminated by six-sided pyramids, the faces of which corre‐ spond with the sides of the prism and form with them the angle of 129°14′. These prisms are usually longer than in case of apatite. It sometimes occurs in small crystalline masses [80],[81]. This variety was former described also as a kind of schorl (NaFe3 2+Al6(Si6O18) (BO3)3(OH)3OH [82],[83]), afterwards as a variety of beryl (Be3Al2Si6O18 [84][85]) [86].

**• Staffelite**: is an obsolete name for a variety of carbonate–fluorapatite from Staffel, Germany, which form nodular-stalactitic aggregates and crusts, of the composition of

**• Voelckerite**: the modern equivalent is oxyapatite (3Ca3(PO4)2·CaO) named according to agricultural chemist J.A. VOELCKER [73], who proved the fact that apatite is often deficient in fluorine and chlorine (**Section 1.4**). Voelckerite is a white, subtranslucent mineral with imperfect cleavage and faint luster. The specific gravity is 3.06, and the hardness on the Mohs scale is about 5. In a thin basal section, a negative uniaxial interference figure was

**• Quercyite**: is an obsolete name for carbonate–hydroxylapatite applied to mixtures of amorphous collophanite (collophane) and crystalline dahllite, francolite, etc. Quercyite is often composed of alternating layers α-quercyite (optically negative) and β-quercyite

**• Wilkeite:** sicicatian strontian apatite [67]. Wilkeite is a former name (EAKLE AND ROGERS [77]

**• Manganapatite:** (manganoan fluorapatite, Mn-bearing fluorapatite) was named by SIEWERT

**• Lasurapatite:** sky blue variety, it occurs in crystals with lapis-lazuli at Bucharei in Siberia

**• Moroxite**: greenish-blue variety of conchoidal apatite (the green varieties are named as asparagus stone). The name moroxite was given to this mineral by Karsten and is bor‐ rowed from the morochites of Pliny, according to author's statement: "*Est gemma, per se*

**• Foliated apatite**: according to the system of mineralogy of JAMESON [81] in which minerals are arranged according to the natural history method, rhomboidal apatite (fist specie) is divided in three subspecies, including (1) foliated apatite, (2) conchoidal apatite and (3)

The most frequent color of foliated apatite is snow-white, yellowish-whiter, reddish-white and greenish-white. Several of these colors occur frequently in the same piece. It sometimes occurs also as massive and disseminated in distinct concretions, which are large and small angulo-granular, and sometimes thin and straight lamellar, generally crystallized. The crystals are small, very small and middle-sized and occur sometimes single, sometimes many irregularly superimposed on each other. It is brittle and easily fragile. Foliated apatite becomes electric by heating and by being rubbed with woolen cloth. On glowing

**• Conchoidal apatite or asparagus**-**stone**: a yellow-green variety of apatite. The name of asparagus stone has been given to this variety in allusion to asparagus green color, which

(optically positive). The density of quercyite ranges from 2.83 to 2.87 g·cm−3 [70].

**• Kurskite**: is an obsolete name for carbonate–fluorapatite23 [75],[76].

12 Apatites and their Synthetic Analogues - Synthesis, Structure, Properties and Applications

in 1914) for a variety of mineral fluorellestadite (**Section 2.4.1**).

coals, it emits a pale grass-green phosphoric light [79]

[78] in allusion to its chemical relationship to fluorapatite.

*porrcea viridisque, trita autem candicans*" [81].

phosphorite described below.

3Ca3(PO4)2·CaF2·CaCO3 [71],[72].

obtained [74].

[79].

In Europe, asparagus stone occurs as a porous iron-shot limestone near Cape de Gate, in Murcia in Spain, in granite near Nantes and is basalt at Mont Ferrier, in France, imbedded in green talc, in the Zillertal in Salzburg, in beds of magmatic ironstone, along with sphere or rutilite (the name is used for almandine, rutile, titanate, or rutilized quartz), calcareous-spar, hornblende, quartz and augite, at Arendal in Norway. In America, it was found imbedded in granite at Baltimore, and in mica-slate in West Greenland [86].


<sup>26</sup> Adjectival modifier that gives some information on the chemistry of the mineral, for example, "sodian," "sodium-rich," "sodium-bearing," or "sodium equivalent of" [93].


The list of calcium phosphate species accepted by Commission on New Minerals and Mineral Names (CNMMN)28 of International Mineralogical Association (IMA) [67] is given in **Table 3**.
