New Mineral with Modular Structure Derived from Hatrurite from the Pyrometamorphic Rocks of the Hatrurim Complex : Ariegilatite , BaCa 12 ( SiO 4 ) 4 ( PO 4 ) 2 F 2 O , from Negev Desert , Israel

Ariegilatite, BaCa12(SiO4)4(PO4)2F2O (R3m, a = 7.1551(6) Å, c = 41.303(3) Å, V = 1831.2(3) Å3, Z = 3), is a new member of the nabimusaite group exhibiting a modular intercalated antiperovskite structure derived from hatrurite. It was found in a few outcrops of pyrometamorphic rocks of the Hatrurim Complex located in the territories of Israel, Palestine and Jordan. The holotype specimen is an altered spurrite marble from the Negev Desert near Arad city, Israel. Ariegilatite is associated with spurrite, calcite, brownmillerite, shulamitite, CO3-bearing fluorapatite, fluormayenite-fluorkyuygenite and a potentially new mineral, Ba2Ca18(SiO4)6(PO4)3(CO3)F3O. Ariegilatite is overgrown and partially replaced by stracherite, BaCa6(SiO4)2[(PO4)(CO3)]F. The mineral forms flat disc-shaped crystals up to 0.5 mm in size. It is colorless, transparent, with white steaks and vitreous luster. Optically, ariegilatite is uniaxial, negative: ω = 1.650(2), ε = 1.647(2) (λ = 589 nm). The mean composition of the holotype ariegilatite, (Ba0.98K0.01Na0.01)Σ1(Ca11.77Na0.08Fe0.06Mn0.05Mg0.04)Σ12(Si3.95Al0.03Ti0.02)Σ4(P1.70C0.16Si0.10S0.03 V0.01)Σ2F2.04O0.96, is close to the end-member formula. The structure of ariegilatite is described as a stacking of the two modules {F2OCa12(SiO4)4} and {Ba(PO4)2} along (001). Ariegilatite, as well as associated stracherite, are high-temperature alteration products of minerals of an early clinker-like association. These alterations took place under the influence of pyrometamorphism by-products, such as gases and fluids generated by closely-spaced combustion foci.

Ariegilatite is named in honor of Dr. Arie Gilat (b.1939).Arie Gilat is retired from the Geological Survey of Israel, where he was involved in geological mapping, tectonics and geochemical studies for more than 30 years.He is the author and co-author of numerous geological papers.At present, his main interests are related to the study of earthquake physics and processes at the core and mantle interface.His continuous support, consulting and several new unconventional ideas on the genesis of the Hatrurim Complex are greatly appreciated by the authors.
Ariegilatite was approved as a new mineral species by Commission on New Minerals, Nomenclature and Classification, International Mineralogical Association (CNMNC IMA) in March 2017 (IMA2016-100).The material was deposited in the mineralogical collection of the Fersman Mineralogical Museum, Leninskiy pr., 18/k2, 115162 Moscow, Russia, Catalogue Number 4956/1.
Raman spectra of ariegilatite were recorded on a WITec alpha 300R Confocal Raman Microscope, WITec, Ulm, Germany (Department of Earth Science, University of Silesia, Sosnowiec, Poland) equipped with an air-cooled solid-state laser (532 nm) and a CCD camera operating at −61 • C. The laser radiation was coupled to a microscope through a single-mode optical fiber with a diameter of 3.5 µm.An air Zeiss LD EC Epiplan-Neofluan DIC-100/0.75NAobjective was used.Raman scattered light was focused on a broad band single mode fiber with an effective pinhole size of about 30 µm, and a monochromator with a 600-mm −1 grating was used.The power of the laser at the sample position was ca.40 mW.Integration times of 5 s with an accumulation of 15-20 scans and a resolution 3 cm −1 were chosen.The monochromator was calibrated using the Raman scattering line of a silicon plate (520.7 cm −1 ).Fitting of spectra was performed with the help of the "GRAMS" program using the mixed Lorentz-Gauss function.
Single-crystal X-ray diffraction data were collected from a crystal of ariegilatite (∼38 × 32 × 25 µm) using synchrotron radiation at the super-bending magnet beamline X06DA at the Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland.The multi-axis goniometer PRIGo [11] and a PILATUS 2M-F detector, which was placed at a distance of 120 mm from the crystal with a vertical offset of 67 mm, was used.The wavelength was set to λ = 0.70848 Å.The data were collected in a single 180 • omega scan with steps of 0.1 • and 0.1-s exposures, controlled by the DA + software [12].Data evaluation and processing was performed using the CrysAlisPro software package [13].As a starting model, the structure of the isostructural analogue nabimusaite was used, adapted to the expected composition.With subsequent analyses of difference-Fourier maps, the structure was refined to R 1 = 1.95%.The refinements include anisotropic displacement-parameters and have been carried out with neutral atom scattering-factors, using the program SHELX97 [14].

Occurrence and Description of Holotype Specimen
Ariegilatite was found in a few outcrops of pyrometamorphic rocks of the Hatrurim Complex located in the territories of Israel, Palestine and Jordan.Investigations of a new mineral were performed in samples of spurrite rocks collected in the Negev Desert (Hatrurim Basin, N31 • 13 E35 • 16 ) near Arad, Israel.Ariegilatite forms strongly flattened crystals of disc-shaped form.In thin-sections, its pseudo-aciculate morphology is usually observed (Figure 1A).The size of some highly-fractured crystals of ariegilatite reaches 0.5 mm with a thickness of 0.1 mm (Figure 1A).Ariegilatite is associated with spurrite, calcite, brownmillerite, shulamitite, CO 3 -bearing fluorapatite, fluormayenite-fluorkyuygenite, periclase, brucite, barytocalcite, baryte, garnets of elbrusite-kerimasite series, unidentified Ca-Fe-and Rb-bearing K-Fe sulfides and a potentially new mineral, Ba 2 Ca 18 (SiO 4 ) 6 (PO 4 ) 3 (CO 3 )F 3 O [15].Ariegilatite is often overgrown and replaced by stracherite (Figure 1B).Ariegilatite and stracherite are usually limited to re-crystallization zones of dark-grey fine-grained spurrite rocks, which differ from the surrounding rocks by discoloration, development of thin calcite veins and also by local appearance of large spurrite metacrysts (up to 1 cm in size), as well as the presence of sulfide mineralization.
of about 30 μm, and a monochromator with a 600-mm −1 grating was used.The power of the laser at the sample position was ca.40 mW.Integration times of 5 s with an accumulation of 15-20 scans and a resolution 3 cm −1 were chosen.The monochromator was calibrated using the Raman scattering line of a silicon plate (520.7 cm −1 ).Fitting of spectra was performed with the help of the "GRAMS" program using the mixed Lorentz-Gauss function.
Single-crystal X-ray diffraction data were collected from a crystal of ariegilatite (∼38 × 32 × 25 μm) using synchrotron radiation at the super-bending magnet beamline X06DA at the Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland.The multi-axis goniometer PRIGo [11] and a PILATUS 2M-F detector, which was placed at a distance of 120 mm from the crystal with a vertical offset of 67 mm, was used.The wavelength was set to λ = 0.70848 Å.The data were collected in a single 180° omega scan with steps of 0.1° and 0.1-s exposures, controlled by the DA + software [12].Data evaluation and processing was performed using the CrysAlisPro software package [13].As a starting model, the structure of the isostructural analogue nabimusaite was used, adapted to the expected composition.With subsequent analyses of difference-Fourier maps, the structure was refined to R1 = 1.95%.The refinements include anisotropic displacement-parameters and have been carried out with neutral atom scattering-factors, using the program SHELX97 [14].

Occurrence and Description of Holotype Specimen
Ariegilatite was found in a few outcrops of pyrometamorphic rocks of the Hatrurim Complex located in the territories of Israel, Palestine and Jordan.Investigations of a new mineral were performed in samples of spurrite rocks collected in the Negev Desert (Hatrurim Basin, N31°13′ E35°16′) near Arad, Israel.Ariegilatite forms strongly flattened crystals of disc-shaped form.In thin-sections, its pseudo-aciculate morphology is usually observed (Figure 1А).The size of some highly-fractured crystals of ariegilatite reaches 0.5 mm with a thickness of 0.1 mm (Figure 1А).Ariegilatite is associated with spurrite, calcite, brownmillerite, shulamitite, CO3-bearing fluorapatite, fluormayenite-fluorkyuygenite, periclase, brucite, barytocalcite, baryte, garnets of elbrusite-kerimasite series, unidentified Ca-Fe-and Rb-bearing K-Fe sulfides and a potentially new mineral, Ba2Ca18(SiO4)6(PO4)3(CO3)F3O [15].Ariegilatite is often overgrown and replaced by stracherite (Figure 1В).Ariegilatite and stracherite are usually limited to re-crystallization zones of dark-grey fine-grained spurrite rocks, which differ from the surrounding rocks by discoloration, development of thin calcite veins and also by local appearance of large spurrite metacrysts (up to 1 cm in size), as well as the presence of sulfide mineralization.corresponds to 4-4.5 on the Mohs scale.In contrast to minerals of the nabimusaite-dargaite series [1,2], ariegilatite does not show pronounced cleavage on (001), and the fracture is irregular.The small size of separated crystal fragments does not allow measuring the density.Therefore, the density was calculated on the basis of structural data and the mean composition of ariegilatite: 3.329 g•cm −3 .Compatibility index 1 − (K p /K c ) = −0.017(superior) was calculated for the empirical formula of ariegilatite of the holotype specimen (Table 1).
Raman and electron microprobe data (Figure 2, Table 1, L15) indicate the presence of small amounts of (CO 3 ) 2− in ariegilatite, replacing (PO 4 ) 3− groups.Refinement of the occupancy factor of P1 (Table 3) shows a small reduction from full occupation (89%), which is in agreement with the substitution by CO 3 .The structural formula of ariegilatite calculated assuming a balanced charge, BaCa 12 (SiO 4 ) 4 {[(PO 4 ) 0.89 0.11 ](CO 3 ) 0.11 } 2 F 1.78 O 1.22 , is close to the empirical formula obtained from microprobe analyses (Table 1, L15).However, the exact location and orientation of the planar CO 3 group cannot be determined from diffraction data.Most likely, replacement of (PO 4 ) 3− by planar (CO 3 ) 2− groups takes place the same way as in stracherite: CO 3 triangles are randomly located along one of the faces of the replaced tetrahedra excluding the face parallel to (001) [10].Replacement of (PO 4 ) 3− by (CO 3 ) 2− in ariegilatite takes place according to the schemes: Ca 2+ + (PO 4 ) 3− ↔ Na + + (CO 3 ) 2− , 2(PO 4 ) 3− ↔ (SiO 4 ) 4− + (CO 3 ) 2− and (PO 4 ) 3 As ariegilatite occurs only in tiny amounts, and the crystals contain numerous inclusions of other phases, useful X-ray powder diffraction data could not be collected.However, a powder pattern was calculated (Table S1) using the model derived from the single-crystal structure refinements.

Occurrences of Ariegilatite in Other Localities of the Hatrurim Complex Rocks
Ariegilatite occurs both in larnite and spurrite rocks of the Hatrurim Complex, whereas minerals of the nabimusaite-dargaite series are found in larnite rocks only [1,2].The first samples of ariegilatite were found in 2011 by M. Murashko in larnite pebble, in the northern part of the Siwaqa pyrometamorphic rock area, 80 km south of Amman, Jordan.Daba-Siwaga is the largest area of the Hatrurim Complex within the Dead Sea rift region [20][21][22].In this samples, ariegilatite is associated with larnite, gehlenite, spinel, fluormayenite, fluorapatite, perovskite and a bredigite-like Ba-bearing mineral (Figure 5A).It forms poikilitic crystals up to 0.25 mm in size and fine reaction rims on fluorapatite (Figure 5A).The mean ariegilatite composition from larnite rock is (Ba 0.96 K 0.02 Na 0.02 ) Σ1 (Ca 11.75 Mg 0.12 Fe 2+ 0.08 Mn 2+ 0.05 ) Σ12 (Si  1, L15).The Raman spectrum of ariegilatite from larnite rocks in Jordan shows no characteristic bands of (CO 3 ) 2− groups (Figure 2, YV595).Furthermore, the calculation of the stoichiometric formula does not indicate the presence of (CO 3 ) 2− (Table 1, YV595).

Discussion
Ariegilatite exhibits an ordered anion distribution.Fluorine and oxygen were assigned to the anion sites utilizing the results of bond valence sum (BVS, Table 5) calculations.Oxygen resides in the center (Figure 3A, blue) and fluorine on the two outer octahedral sites (Figure 3A, green) of the antiperovskite module.New BVS calculations revealed the same preference in nabimusaite, where one fluorine atom seems to be distributed over the two outer octahedral sites, in contrast to what has been reported before [1,2,25].Fluorine may enter the central octahedra when the charge is compensated as, for example, in arctite BaCa 7 Na 5 (PO 4 ) 6 F 3 [6,8], where Ca atoms (of the central octahedra) are substituted by sodium.Similar behavior is observed in the isostructural synthetic compound Ca 5.45 Li 3.55 [SiO 4 ] 3 O 0.45 F 1.55 [26], where the outer octahedral sites are occupied by fluorine, whereas the inner site seems to be shared by oxygen and fluorine.For charge compensation, the Ca-sites coordinating the inner octahedral site are partly substituted by lithium.
So far, ariegilatite shows the highest fluorine content (>3 wt %, Table 1) of all members of the nabimusaite group.It occurs in spurrite, as well as in larnite rocks (Figures 1 and 5).Ariegilatite from spurrite rocks contain significant amounts of (CO 3 ) 2− (Table 1).It forms relatively large poikilitic crystals standing out against a fine-grained matrix and grows after fluorapatite (Figures 1 and 5).Minerals of the dargaite-nabimusaite series (and also gazeevite), as well as minerals of the ternesite-silicocarnotite series and jasmundite are high-temperature alteration products of minerals of an early clinker-like association of larnite rocks.These alterations took place under the influence of pyrometamorphism by-products, such as gases and fluids generated by closely-spaced combustion foci [1,28,29].
In our understanding, ariegilatite, as well as associated stracherite are the products of high-temperature alteration of early pyrometamorphic rocks with increased phosphorus (fluorapatite) and decreased sulfur (absence of fluorellestadite and ye'elimite) contents under the influence of high-fluorine, CO 2 -bearing fluids/gases.Transport of these fluids/gases is realized through cracks and micro-channel nets (Figure 5F), which may have existed for a long time in heated pyrometamorphic rocks.

Figure 4 .
Figure 4. Using a cation-centered representation of the ariegilatite structure (A-C), the antiperovskite module can be decomposed into four layers assembled of triplets of Ca coordination polyhedra.Structural voids within each layer accommodate the silicate tetrahedra.Perpendicular through the layers, columns of four Ca-triplets can be identified.These are shown in a projection along c and [010] in (B).The layers of Ca-triplets are connected by common anions in octahedral coordination: Ca1 and Ca2 layers are sharing F1; Ca2 and Ca2 are connected by O7.In (C), two layers of Ca-triplets are removed at the top half of the image.

Figure 4 .
Figure 4. Using a cation-centered representation of the ariegilatite structure (A-C), the antiperovskite module can be decomposed into four layers assembled of triplets of Ca coordination polyhedra.Structural voids within each layer accommodate the silicate tetrahedra.Perpendicular through the layers, columns of four Ca-triplets can be identified.These are shown in a projection along c and [010] in (B).The layers of Ca-triplets are connected by common anions in octahedral coordination: Ca1 and Ca2 layers are sharing F1; Ca2 and Ca2 are connected by O7.In (C), two layers of Ca-triplets are removed at the top half of the image.

Figure 4 .
Figure 4. Using a cation-centered representation of the ariegilatite structure (A-C), the antiperovskite module can be decomposed into four layers assembled of triplets of Ca coordination polyhedra.Structural voids within each layer accommodate the silicate tetrahedra.Perpendicular through the layers, columns of four Ca-triplets can be identified.These are shown in a projection along c and [010] in (B).The layers of Ca-triplets are connected by common anions in octahedral coordination: Ca1 and Ca2 layers are sharing F1; Ca2 and Ca2 are connected by O7.In (C), two layers of Ca-triplets are removed at the top half of the image.

Table 4 .
Anisotropic displacement parameters U ij for ariegilatite.