**2.1.3. Phosphohedyphane**

Fluorphosphohedyphane is found in cracks and narrow veins in highly siliceous hornfels3

fluorapatite, goethite, gypsum, mimetite, opal (SiO2·*n*H2O [11],[12]), phosphohedyphane, plumbogummite (PbAl3(PO4)(PO3OH)(OH)6 [13],[14],[15]), plumbophyllite (Pb2Si4O10·H2O [16]), plumbotsumite (Pb5Si4O8(OH)10 [17],[18],[19], pyromorphite (**Section 1.6.4**), quartz and wulfenite (PbMoO4 [20]). The streak of the new mineral is white; the luster is subadamantine [8]. The structure and the crystal habit of fluorphosphohedyphane hedyphane are shown in

**Fig. 7** The structure (perspective view along the *c*-axis), the coordination of Pb with likely approximate location of

Fluorphosphohedyphane has the apatite structure with the ordering of Ca and Pb in two cation sites, as in hedyphane and phosphohedyphane. The Pb2+ cation exhibits a stereoactive 6*s*<sup>2</sup> lone

of 2.867 Å to Pb atoms, in contrast to six Pb-Cl bonds of 3.068 Å in phosphohedyphane. For

 The name for this type of contact metamorphic rock was given by K. VON LEONHARDT. The name originates from the designation of the highest peaks in the Alps but it can be also derived from ancient mining term from Saxony (Germany) which was used to describe hard, compact metamorphic rock developed at the margin of an igneous body. These rocks possess outstanding toughness due to fine-grained nonaligned crystals of platy or prismatic habit. Hornfels are sometimes banded, but their texture can be also porphyroblastic, i.e. they occur as large crystals within fine ground groundmass of

 The name of the mineral comes from the Greek words *chyrosos* (gold) and *kolla* (glue). The mineral is also named as bisbeeite (blue mineral of the composition of (Cu,Mg)SiO3·nH2O named after Bisbee Cochise County, Arizona). <sup>5</sup> In the clinographic projection the crystal is turned by angle *Θ* around a vertical axis in order to make the front- and the

activity that causes the Jahn–Teller geometry distortion, specific optical properties, and ferroelectricity. Lone electron pair is also used for the explanation of anisotropies of thermal expansion coefficient, piezoelectric and elastic properties,

6p2

[21] (**Fig. 7**). The *Z* anion site at (0, 0,½) is fully occupied by *F* forming six bonds

. Cations with formal ns2

np6

electronic configuration usually

lone pair is responsible for the stereochemical

lone-electron pair and the crystal habit of fluorphosphohedyphane in clinographic projection5

right-hand faces visible. Other forms are orthographic projection and perspective projection.

The electronic configuration for Pb is [Xe] 4f14 5d10 6s2

display novel properties and it is widely believed that the so-called n*s*<sup>2</sup>

in association with cerussite1, chrysocolla4

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

**Fig. 7**.

electron pair6

metamorphic rock [9].

and optoelectronic properties [21].

3

4

6

[9]

((Cu2−*<sup>x</sup>*Al*x*)H2−*<sup>x</sup>*Si2O5(OH)4·*n*H2O [10]), fluorite,

[8].

Phosphohedyphane (Ca2Pb3(PO4)3Cl [1],[22]): the mineral from the Capitana mine, Copiapó, Atacama Province, Chile, discovered in 2004. Known localities for the mineral phosphohedy‐ phane are introduced in **Fig. 8**. Phosphohedyphane is brittle with subconchoidal fracture and no cleavage. Phosphohedyphane is hexagonal with the space group P63/M and the cell parameters *a* = 9.857, *c* = 7.13 Å, *V* = 599.94 Å<sup>3</sup> and *Z* = 2. The hardness of the mineral on the Mohs scale is 4. The mineral is closely associated with quartz, duftite (PbCuAsO4(OH) [23]) and bayldonite (Cu3PbO(AsO3OH)2(OH)2 [24]).


**Fig. 8** Known localities for the mineral phosphohedyphane.

**Fig. 9** The structure (perspective view along the *c*-axis), the coordination of Pb with approximate location of lone-elec‐ tron pair and the crystal habit of phosphohedyphane [22].

The mineral is a phosphate analogue of hedyphane and possesses an apatite structure with the ordering of Ca and Pb in two nonequivalent large cation sites. The structure refinement indicates that the Ca(2) sites are completely occupied by Pb and the Ca(1) sites contain 92% Ca and 8% Pb. The tetrahedral site refines to 91% P and 9% As. The refinement indicates the 0,0,0 position to be fully occupied by Cl. The structure and the crystal habit of phoshohedyphane are shown in **Fig. 9**.

Other secondary minerals identified in the oxidized zone together with phosphohedyphane are: anglesite (PbSO4 [25]), arsentsumebite (Pb2Cu(AsO4)(SO4)(OH) [26],[27]), azurite (Cu3(CO3)2(OH)2 [28]), beaverite7 (PbCu2+Fe3+2(SO4)2(OH)6 [29],[30],[31]), calcite (CaCO3, hexagonal with the space group R3 ¯C 8 [32]), cerussite, mimetite (**Section 1.6.7**), malachite (Cu2CO3(OH)2 [33]), mottramite and perroudite (Ag4Hg5S5(I,Br)2Cl2 [34]) [22].

#### **2.1.4. Morelandite**

Morelandite (Ca2Ba3(AsO4)3Cl, (Ba, Ca, Pb)5(AsO4, PO4)3Cl [1],[35],[36]), is a mineral that was named in 1978 according to MORELAND. It occurs as small irregular masses associated with hausmannite (Mn2+Mn3+2O4 [37]) and calcite in the Jakobsberg mine, near Nordmark, Sweden (**Fig. 10**). The structure of morelandite is shown in **Fig. 11**.

<sup>7</sup> The minerals beaverite-(Cu) and beaverite-(Zn), i.e. PbZnFe3+2(SO4)2(OH)6 [29], were recognized. Beaverite is an old name for the mineral beaverite-(Cu).

<sup>8</sup> There is also an orthorhombic polymorph (PMCN) aragonite.

**Fig. 10** Known locality of the mineral morelandite.

**Fig. 11** The structure of morelandite (perspective view according to the *c*-axis).

The mineral is gray to light yellow with white streaks, greasy to vitreous luster, and shows poor cleavage on {001}. Morelandite is hexagonal with the space group P63/M and the cell parameters *a* = 10.169, *c* = 7.315 Å, *V* = 655.09 Å3 and *Z* = 2. The hardness of the mineral on the Mohs scale is 4½.

#### **2.1.5. Aiolosite**

**Fig. 9** The structure (perspective view along the *c*-axis), the coordination of Pb with approximate location of lone-elec‐

The mineral is a phosphate analogue of hedyphane and possesses an apatite structure with the ordering of Ca and Pb in two nonequivalent large cation sites. The structure refinement indicates that the Ca(2) sites are completely occupied by Pb and the Ca(1) sites contain 92% Ca and 8% Pb. The tetrahedral site refines to 91% P and 9% As. The refinement indicates the 0,0,0 position to be fully occupied by Cl. The structure and the crystal habit of phoshohedyphane

Other secondary minerals identified in the oxidized zone together with phosphohedyphane are: anglesite (PbSO4 [25]), arsentsumebite (Pb2Cu(AsO4)(SO4)(OH) [26],[27]), azurite

Morelandite (Ca2Ba3(AsO4)3Cl, (Ba, Ca, Pb)5(AsO4, PO4)3Cl [1],[35],[36]), is a mineral that was named in 1978 according to MORELAND. It occurs as small irregular masses associated with hausmannite (Mn2+Mn3+2O4 [37]) and calcite in the Jakobsberg mine, near Nordmark,

The minerals beaverite-(Cu) and beaverite-(Zn), i.e. PbZnFe3+2(SO4)2(OH)6 [29], were recognized. Beaverite is an old

¯C 8

Sweden (**Fig. 10**). The structure of morelandite is shown in **Fig. 11**.

There is also an orthorhombic polymorph (PMCN) aragonite.

(Cu2CO3(OH)2 [33]), mottramite and perroudite (Ag4Hg5S5(I,Br)2Cl2 [34]) [22].

(PbCu2+Fe3+2(SO4)2(OH)6 [29],[30],[31]), calcite (CaCO3,

[32]), cerussite, mimetite (**Section 1.6.7**), malachite

tron pair and the crystal habit of phosphohedyphane [22].

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

are shown in **Fig. 9**.

**2.1.4. Morelandite**

name for the mineral beaverite-(Cu).

7

8

(Cu3(CO3)2(OH)2 [28]), beaverite7

hexagonal with the space group R3

Aiolosite (Na2(Na2Bi)(SO4)3Cl, ideally Na4Bi(SO4)3Cl [7]): hexagonal mineral with the space group P63/M and the cell parameters *a* = 9.626, *c* = 6.88 Å, *V* = 552.09 Å3 and *Z* = 2. The calcu‐ lated density of the mineral is 3.59 g·cm−3. Aiolosite is a sulfate mineral isotopic with apatite, which was found in an active medium-temperature intracrater fumarole at La Fossa crater, Vulcano Island, Aeolian archipelago, Sicily, Italy (**Fig. 12**). It occurs as acicular to slender prismatic crystals up to 0.5 mm long in an altered pyroclastic breccia (refer to **Footnote 27** in **Section 1.1**), together with alunite, anhydrite (CaSO4 [38]), demicheleite-(Br) (BiSBr [39]), bismuthinite (Bi2S3 [40]) and panichiite ((NH4)2SnCl6 [41]). Aiolosite is colorless to white, with white streaks and nonfluorescent. The luster is vitreous.

**Fig. 12** The locality of the mineral aiolosite.

The structure of the mineral aiolosite is shown in **Fig. 13**.

The structure of aiolosite shows two independent cationic sites M(1) and M(2). Due to close similarity in ionic radii of Na+ and Bi3+, Bi exclusively prefers the M(2) site instead of M(1), which can be ascribed mainly to the Coulombic effect, in view of the higher charge of Bi3+ compared to Na+ , since the average M(2)-O distance (2.516 Å) is shorter than that of M(1)-O (2.617 Å). A similar effect also affects the distribution of Na+ and Ca2+ sites in cesanite (**Section 2.1.7**) [7].

**Fig. 13** The structure of aiolosite (perspective view according to the *c*-axis).

#### **2.1.6. Caracolite**

Caracolite (Na2(Pb2Na)(SO4)3Cl, sodium lead hydroxylchlorosulfate [1],[42],[43],[44]), is a vitreous colorless or grayish mineral from Beatriz mine, Caracoles, Chile, which was report‐ ed by WEBSKY in 1886. Known localities and the structure of the mineral caracolite are shown in **Fig. 14**. It occurs as crystalline incrustations with imperfect pseudohexagonal crystals up to 1 mm large. The crystals have the form of hexagonal pyramids with the base and the prism, but they are supposed to be pseudohexagonal. The mineral exhibits complex polysynthetic twinning with rather large extinction angles.


**Fig. 14** The localities of the mineral aiolosite.

**Fig. 12** The locality of the mineral aiolosite.

compared to Na+

(**Section 2.1.7**) [7].

**2.1.6. Caracolite**

The structure of the mineral aiolosite is shown in **Fig. 13**.

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

**Fig. 13** The structure of aiolosite (perspective view according to the *c*-axis).

twinning with rather large extinction angles.

The structure of aiolosite shows two independent cationic sites M(1) and M(2). Due to close similarity in ionic radii of Na+ and Bi3+, Bi exclusively prefers the M(2) site instead of M(1), which can be ascribed mainly to the Coulombic effect, in view of the higher charge of Bi3+

(2.617 Å). A similar effect also affects the distribution of Na+ and Ca2+ sites in cesanite

Caracolite (Na2(Pb2Na)(SO4)3Cl, sodium lead hydroxylchlorosulfate [1],[42],[43],[44]), is a vitreous colorless or grayish mineral from Beatriz mine, Caracoles, Chile, which was report‐ ed by WEBSKY in 1886. Known localities and the structure of the mineral caracolite are shown in **Fig. 14**. It occurs as crystalline incrustations with imperfect pseudohexagonal crystals up to 1 mm large. The crystals have the form of hexagonal pyramids with the base and the prism, but they are supposed to be pseudohexagonal. The mineral exhibits complex polysynthetic

, since the average M(2)-O distance (2.516 Å) is shorter than that of M(1)-O

**Fig. 15** The structure of caracolite (perspective view according to the *c*-axis).

Caracolite is monoclinic mineral with the space group P21/M and the cell parameters *a* = 19.62, b = 7.14, *c* = 9.81 Å and *β* = 120°, *V* = 1190.14 Å3 , *Z* = 4. Calculated density is 4.50 g·cm−3. The hardness of the mineral on the Mohs scale is 4½. The structure of caracolite is shown in **Fig. 15**.

#### **2.1.7. Cesanite**

Cesanite (Ca2Na3(SO4)3OH [45],[46],[47]) is a colorless, medium to coarse-grained, soft mineral which occurs both as a solid vein (1 cm thick) and as cavity-filling of an explosive breccia in core samples of the Cesano-I geothermal well (Cesano area, Latium, Italy). Cesanite was recognized as new mineral by CAVARRETA et al [47]. The crystal structure determination confirms that cesanite has to be considered a member of the apatite-wilkeite-ellestadite series, where (PO4) 3− is entirely substituted by (SO4) 2−, the charge balance being made up by partial substitution of Na+ for Ca2+ and H2O for (OH<sup>−</sup> , Cl<sup>−</sup> , F<sup>−</sup> ).

The general formula of this series, proposed by HARADA et al [48] and modified by CAVARRE‐ TA et al [47], is as follows:

$$\text{Ca}\_{5-w}\text{Na}\_w(\text{Si}\_{y\text{.}}\text{S}\_{z\text{.}}\text{P}\_{3-y-z})\text{O}\_{12}\text{(F}\_{\text{.}}\text{ Cl, OH}\text{)}\_x\text{nH}\_2\text{O}\_7$$

where *w* = 1 – *x* – *y* + *z* and *n* ≤ 1 – *x*.

Cesanite is a hexagonal mineral with the space group P6 ¯ and the cell parameters *a* = 9.463, *c* = 6.9088 Å, *V* = 535.79 Å3 and *Z* = 1. Calculated density of the mineral is 2.75 g·cm−3. The hardness of the mineral on the Mohs scale ranges from 2 to 3.

The structure of cesanite is shown in **Fig. 16**. Synthetic and natural cesanite show typical elements of the apatite structure, but the reduction of symmetry from the centrosymmetric space group P63/M to the noncentrosymmetric space group P6 ¯ leads to a doubling ofthe number of crystallographically independent sites. Na and Ca cations are distributed over four independent sites. They are coordinated either by six O atoms and one hydroxyl ion or by water molecule (M(1), M(2)) or nine O atoms (M(3), M(4)) [46].

**Fig. 16** The structure of cesanite (perspective view according to the *c*-axis; a), crystal habit (b) and the coordination polyhedra for M(1) (1), M(2) (2), M(3) (3) and M(4) (4) in synthetic analogue of the mineral cesanite (c) [47].
