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In the Mănăila alpine area, the soil layer developed in situ on top of the sericite-schists, which belong to the Tulghes 3 metamorphic unit. The aim of the present work was to determine the degree of soil formation using both mineralogical and geochemical exploration methods. XRD, FTIR and SEM-EDS results showed that the soil constituents were dioctahedral 2:1 minerals, quartz, chlorite, Na-feldspar, rutire and ilmenite. Mainly illite and secondarily mixed-layer minerals were considered to be the most likely minerals resulting from the transformation of sericite and chlorite under acidic alpine conditions. Geochemical modeling inferred the dominance of illite and the presence of smectite as a chlorite alteration product. The weathering indices supported the moderate stage of the soil development agreeing with mineralogical observations. Because of the abundance of sericite and quartz in the parent material, the soil formation was retarded, and its present composition is still related to the bedrocks.

International audience; Nearly 300 million t of phosphogypsum (PG) are produced every year as a byproduct from phosphate fertilizer production worldwide. Approximately 58% of the PG are stacked, 28% are discharged in coastal waters and only 14% are further processed. This critical review provides an overview of the physical-chemical properties of PG produced from sedimentary and magmatic phosphate ore worldwide using various analytical tools. Results from more than 25 years of work on PG at École des Mines de Saint-Étienne are presented and critically discussed. In total PG samples from 67 industrial storage sites around the world and PG samples synthesized under different conditions in the laboratory have been considered. The low radioactivity present in PG (particularly PG produced from sedimentary phosphate rock) was identified as the main challenge to using PG as a raw material in construction. Water-soluble and volatile chemical compounds were identified as the main challenge to environmentally sound PG management. Although PG does (in most cases) not pose an immediate threat to the environment the authors recommend processing all PG instead of storing or disposing it, to eliminate potential long-term risks and utilize a relevant secondary resource.

A rich association of primary guano minerals, including taranakite, hydroxylapatite, brushite and gypsum with relicts of illite, kaolinite, alpha (low) quartz and calcite, was identified in the fossil bat guano deposit from Gura Dobrogei Cave, Dobrogea County, Romania. Gypsum and Ca phosphates developed preferentially on the carbonate bedrock or on fallen carbonate blocks in the guano mass, whereas taranakite was identified in the clay-rich, detritic sequences. The mineral species from the cave were characterized by optical methods, scanning electron microscopy, X-ray powder diffraction, Fourier-transform infrared and inductively coupled plasma–atomic emission spectrometry analysis. Chemically induced local dehydration of primary minerals, characterized by low temperatures (up to 100 ∘C or even lower) and critically depending on exothermal reactions in the guano mass, prompted the formation of a secondary association, consisting of francoanellite, bassanite and monetite. Topotactic substitutions were observed in the cases of francoanellite on taranakite, bassanite on gypsum and monetite on brushite. In its turn, ardealite was partially replaced by monetite and bassanite. The sequential dehydration process seems driven by the degradation of organic matter by microbial action and also, presumably, by other exothermic reactions at local scale (e.g., oxidation of ammonia, allogenic pyrite or other organic compounds).

Material from the type locality, the “dry” Cioclovina Cave, Sureanu Mountains, Romania, was re-examined in order to update the descriptive mineralogy of ardealite, a rare hydrated calcium acid phosphate sulfate. Ardealite from Cioclovina has a S/P ratio ranging between 1/0.87 and 1/0.98. Although S remains the main tetrahedral cation in the structure, P is consistently present at concentrations between 19.10 and 20.45 wt% P 2 O 5 (0.928–0.992 P atom per formula unit). Concerning the other cations, the mineral shows a very restricted range of composition, without Fe and with very low Mn, Mg, Na and K contents. The indices of refraction are α = 1.530(2), β = 1.537(2) and γ (calculated for 2 V γ = 86°) = 1.543. The measured density [ D m = 2.335(3)–2.342(5) g/cm 3 ] agrees well with the calculated values [ D x = 2.317–2.350 g/cm 3 ]. The average unit-cell parameters refined from 31 sets of X-ray powder diffraction data are a = 5.719(5), b = 31.012(28), c = 6.249(7) A and β = 117.21(6)°. Thermally assisted X-ray diffraction analyses confirm that water is lost in three steps; the loss of molecular water is a two-step process and is complete below 250 °C. The first thermal breakdown products are brushite and bassanite. The band multiplicity on the IR-absorption spectrum (3 ν 3 + 1 ν 1 + 3 ν 4 + 2 ν 2 ) suggests that the protonated phosphate and sulfate groups have C s point symmetry. The mineral derives from the reaction between calcium carbonate from the moonmilk flows or the cave floor and phosphoric solutions derived from bat guano, with or without hydroxylapatite as a precursor, at pH values up to 5.5.

A shallow-level monzodioritic to quartz-monzodioritic pluton of the Upper Cretaceous age caused contact metamorphism of Tithonic&ndash, Kimmeridgian reef limestones at Măgureaua Vaţei (Metaliferi Massif, Apuseni Mountains, Romania). The preserved peak metamorphic assemblage includes gehlenite (Ak 33.64&ndash, 38.13), monticellite, wollastonite-2M, Ti-poor calcic garnet, and Ca-Tschermak diopside (with up to 11.15 mol.% Ca-Tschermak molecule). From the monzodioritic body to the calcitic marble, the periplutonic zoning can be described as: monzodiorite/agpaitic syenite-like inner endoskarn/wollastonite + perovskite + Ti-poor grossular + Al-rich diopside/wollastonite + Ti-poor grossular + diopside + vesuvianite/gehlenite + wollastonite + Ti poor grossular + Ti-rich grossular (outer endoskarn)/wollastonite + vesuvianite + garnet (inner exoskarn) / wollastonite + Ti-rich garnet + vesuvianite + diopside (outer exoskarn)/calcitic marble. Three generations of Ca garnets could be identified, as follows: (1) Ti-poor grossular (Grs 53.51&ndash, 81.03 mol.%) in equilibrium with gehlenite, (2) Ti-rich grossular (Grs 51.13&ndash, 53.47 mol.%, with up to 19.97 mol.% morimotoite in solid solution), and (3) titanian andradite (Grs 32.70&ndash, 45.85 mol.%), with up to 29.15 mol.% morimotoite in solid solution. An early hydrothermal stage produced retrogression of the peak paragenesis toward vesuvianite, hydroxylellestadite (or Si-substituted apatite), clinochlore, &ldquo, hibschite&rdquo, (H4O4-substituted grossular). A late hydrothermal event induced the formation of lizardite, chrysotile, dickite, thaumasite, okenite and tobermorite. A weathering paragenesis includes allophane, C-S-H gels and probably portlandite, unpreserved because of its transformation in aragonite then calcite. Overprints of these late events on the primary zoning are quite limited.

The high-temperature skarn of Cornet Hill (Apuseni Mountains, Romania) is known as one of the rare occurrences of spurrite and tilleyite worldwide. Both minerals concentrate in the outer skarn zone, corresponding to the exoskarn, at the contact between a monzodiorite-quartz monzonite body of Upper Cretaceous age and Tithonic-Kimmeridgian reef limestones. The Cornet Hill skarn is clearly zoned. The zoning is defined by the predominance of series of mineral species and is, from the outer to the inner part of the metasomatic area, as follows: calcite (marble), tilleyite, spurrite, wollastonite + gehlenite + vesuvianite, wollastonite + grossular, quartz monzonite. The exoskarn is confined to the tilleyite- and spurrite-bearing zones. The mineral associations identified in the exoskarn zone so far include: (1) metasomatic or primary products such as spurrite, tilleyite, and accessory gehlenite, grossular, titanian andradite, monticellite, wollastonite, perovskite, vesuvianite, ellestadite-(OH), and (2) hydrothermal and weathering (secondary) minerals such as afwillite, fukalite, scawtite, thaumasite, hibschite, xonotlite, thomsonite, gismondine, plombierite, tobermorite, riversideite, portlandite, allophane, calcite, and aragonite. Chemical, optical, infrared absorption, and X-ray powder analyses of the primary mineral species, as well as of three secondary species firstly described in the Romanian skarns, i.e. , afwillite, thaumasite, and fukalite, are reported here.

Gehlenite is a common mineral in three high-temperature calcic skarns in Romania: Magureaua Vaţei and Cornet Hill in Apuseni Mountains and Oraviţa in Banat. In all three occurrences, a gehlenite zone occurs within the contact between dioritic or monzodioritic bodies of Upper Cretaceous age and carbonaceous sequences of Mesozoic age. The melilite solid-solutions vary from Ak 34.1 to Ak 51.2 (mean Ak 41.2 ) at Oraviţa, from Ak 30.4 to Ak 42.9 (mean Ak 38.3 ) at Magureaua Vaţei, and from Ak 24.3 to Ak 41.7 (mean Ak 32.9 ) at Cornet Hill, respectively. The content of “Na-melilite” is low, from up to 1.96 mol.% at Cornet Hill to up to 3.60 mol.% at Oraviţa. The cell parameter a ranges from 7.679(3) to 7.734(3) A at Oraviţa, from 7.683(4) to 7.735(1) A at Magureaua Vaţei, and from 7.684(3) to 7.733(1) A at Cornet Hill, whereas c varies from 5.043(3) to 5.065(3) A at Oraviţa, from 5.040(1) to 5.070(3) A at Magureaua Vaţei, and from 5.044(1) to 5.067(4) A at Cornet Hill. It is not possible to quantify the variations in the crystallographic parameters by considering only the akermanitic substitution because the “Na-melilite” and “Fe-akermanite” substitutions also play an important role. The cell parameter a remains practically constant within experimental errors, in spite of the increasing akermanite-for-gehlenite substitution, due to the opposite influence of the “Na-melilite” component. The akermanite substitution prevails over the opposite influence of “Na-melilite” in increasing the cell volume, and is additive to the influence of “Na-melilite” in decreasing the cell parameter c . The record in the infrared-absorption spectra of bands located at ~855 cm −1 and ~670 cm −1 , respectively, which may be tentatively assigned to Al–O–Al stretching, is indicative of the presence of gehlenite-rich members of the melilite group in all the three occurrences.

In this paper we intend to show results from the mineralogical analyses performed on samples from three caves in the Baile Herculane area. All minerals presented here are described for the first time in the cave from which they were sampled.

After diffractometric X-ray analyses through the powder method, made on sampling tests from two caves in the Perşani Mountains karst, mineral associations made up of calcite, magnesium calcite, aragonite, dolomite, brushite, hydroxylapatite, carbonate-hydroxylapatite, gypsum and α-quartz were emphasized. Tables arepresented with the resulting data from the diffractometric analyses, including the computed parameters of the elementary cells of each mineral species. The materials are discussed comparatively with the existent data in the literature. In the final chapter there is a discussion upon the mineralogenesis of the determined species.

By means of RX and IR analyses we emphasize an associations of minerals in Peştera Liliecilor (Liliecilor Cave) from the Olteţului Gorges made up by hydroxylapatite,carbonate-hydroxylapatite, ardealite, brushite and gypsum as the main minerals and quartz and illite as secondary minerals. In the final part of the paper, the authors present some opinions about the possible genesis of the mineral species.

International audience; A shallow-level dioritic pluton of Upper Cretaceous age caused extensive contact metamorphism of a Mesozoic calcareous sequence at Oraviţa-Ciclova in Romania. The peak metamorphic assemblage (stage I) includes wollastonite, åkermanite-rich melilite, Ti-rich calcic garnet, and pyrrhotite. A second, subsequent paragenesis (stage II) is due to local decreases in fluid pressure and includes gehlenite, Ti-poor calcic garnet, monticellite, Al-rich diopside, magnetite, perovskite, and probably a Ca-Si mineral (kilchoanite?). An early hydrothermal stage (stage III) produced retrogression of the first two stages and a paragenesis including vesuvianite, clintonite, fukalite, katoite, and hydroxylellestadite. A second, late hydrothermal event (stage IV) resulted in the formation of clinochlore, talc, epidote, zeolites (scolecite and thomsonite-Ca), thaumasite, and tobermorite. A last, weathering, paragenesis corresponding to stage V includes allophane (C-S-H gels) and probably portlandite, unpreserved because of its transformation to aragonite, then calcite. The peak metamorphic conditions during the prograde evolution are estimated to have been 750–800 °C for a fluid pressure of up to 0.5 kbar. The main constants determined from chemical, optical, and X-ray powder analyses of these mineral species are reported here. This work documents the first occurrence of katoite and the second occurrences of perovskite, fukalite, and hydroxylellestadite in the Romanian skarns.

In a recent work, Onac and White (2003) reported on berlinite, but also chlorellestadite and churchite, from the Bivouac Room, Cioclovina Cave, Romania. Our analyses of materials collected from this site failed to identify berlinite, chlorellestadite, or churchite. Due to the nature of the samples collected from the bat guano deposit at Cioclovina, many possible sources of confusion can occur. For example, separates from a mixture of taranakite, quartz, and minor illite could give the same analytical results as those reported by Onac and White (2003) for "berlinite". For this reason, we consider that the occurrence of berlinite at Cioclovina, as well as the occurrence of other exotic species such as chlorellestadite or churchite, is not well enough substantiated and their report must be regarded with caution. Arguments to support this point of view are problems identified with the analytical techniques (EMPA, XRD), the failure of the experimental synthesis of berlinite in "dry" conditions at atmospheric pressure, and the geochemical context from Cioclovina.

This paper documents the chemistry, physical properties, thermal and infrared behavior and unit-cell parameters of taranakite in the "dry" Cioclovina Cave, which is the second documented occurrence of this mineral in Romania. The mineral occurs as earthy white nodules scattered throughout the terra rossa mass. Associated minerals are low (alpha) quartz and scarce illite. Individual crystals do not exceed 7μm in diameter, are roughly hexagonal and tabular on (0001). The indices of refraction are e = 1.508(1) and to = 1.502(1). The measured density [D m = 2.11(1) g/cm 3 agrees well with the calculated value [D x = 2.133 g/cm 3 ]. A wet-chemical analysis yielded (in wt.%): K 2 O = 9.06, Na 2 O = 0.11, (NH 4 ) 2 O = 0.33, MnO = 0.02, MgO = 0.07, CaO = 0.31, Al 2 O 3 = 18.78, Fe 2 O 3 = 0.34, P 2 O 5 = 42.32, H 2 O = 28.30, total 99.64, which leads to the chemical-structural formula: [K 2 . 5 8 1 Na 0 . 0 4 1 (NH 4 ) 0 . 1 6 9 Ca 0 . 0 7 4 Mg 0 . 0 2 3 Mn 0 . 0 0 4 ](Al 4 . 9 4 2 Fe 0 . 0 5 7 )(PO 4 ) 1 . 9 9 (HPO 4 ) 6 . 0 1 18.07H 2 O. The hexagonal cell parameters refined from three sets of X-ray powder data are a = 8.687(9)A, c = 95.69(5)A, V = 6254(16)A 3 , a: c = 0.091:1. Thermal analyses showed that the molecular water is lost in two steps, before 200°C; the dehydration is complete at 365°C. The band multiplicity on the IR-absorption spectrum suggests that the protonated and unprotonated phosphate groups have C 3 and C 3 v punctual symmetries, respectively, whereas the strong imprint of the bands assumed to P-O-H vibrations suggests the local presence of (H 2 PO 4 ) - groups. Taranakite from Cioclovina is authigenic and crystallized through the in situ fixation of the potassium and aluminum ions derived from a clay precursor into a phosphate structure.

International audience; Apatite-(CaOH) is the most abundant phosphate in the deposit of fossil bat guano in the “dry” Cioclovina Cave, Şureanu Mountains, South Carpathians, Romania. Initial deposits, of both biogenic and authigenic origin, were chemically equilibrated during diagenesis. Individual crystals are tabular, roughly hexagonal, platy on (0001) and usually between 3 and 15 µmm across and up to 1 µmm thick. The mean indices of refraction measured for 10 representative samples are &#949 1.645(2) and &#969 1.653(1). The mean measured density [Dm = 3.17(2) g/cm3] is in good agreement with the individual calculated values. The unit-cell parameters calculated as average of 20 sets of values are a 9.436(13), c 6.868(8) Å. The mineral is Ca-deficient, carbonate- and sulfate-bearing. Less than 2.26% of the phosphate groups are protonated, and less than 4.66% are replaced by sulfate. The cumulative incorporation of other cations in the Ca sites accounts for only 0.71 to 4.07% (mean 2.07%). Both unit-cell parameters and thermal behavior are characteristic for a hydrous A-type carbonated apatite-(CaOH), with molecular H2O and carbonate substituting for hydroxyl in the structural channels. The multiplicity of the bands in the infrared absorption spectrum (3&#9573 + 1&#9571 + 3&#9574 + 2&#9572) is consistent with a C6 point symmetry of the phosphate anion. Whitlockite obtained by thermal breakdown at 1000°C is sulfate-bearing. The authigenesis of the Cioclovina apatite-(CaOH) involved a reaction between calcium carbonate from the moonmilk flows or the cave floor and phosphoric solutions derived from guano, with brushite or an X-ray amorphous phase as a precursor.; L’apatite-(CaOH) est le phosphate le plus abondant du dépôt fossile de guano de chauve-souris de la grotte «sèche» de Cioclovina, monts Şureanu, Carpates Méridionales, en Roumanie. Les dépôts initiaux, d’origine aussi bien biogène qu’authigène, ont été portés à l’équilibre chimique durant la diagenèse. Les individus cristallins sont tabulaires, vaguement hexagonaux, aplatis selon (0001). En général, ils ont entre 3 et 15 µmm de diamètre et une épaisseur jusqu’à 1 µmm. Les indices de réfraction moyens, mésures sur 10 échantillons représentatifs, sont &#949 1.6451,645(2) et &#969 1,653(1). La densité mesurée moyenne [Dm = 3.17(2) g/cm3] concorde bien avec les valeurs de densité calculées. Les paramètres réticulaires, obtenus comme moyenne de 20 déterminations de valeurs individuelles, sont a 9.436(13) et c 6.868(8) Å. Le minéral est déficitaire en Ca et contient du carbonate et du sulfate. Jusqu’à 2.26% des groupes phosphate sont protonés et jusqu’à 4.66% sont remplacés par des groupes sulfate. Le remplacement du Ca par d’autres cations est mineur, ne comptant que pour 0.71 à 4.07% des sites occupés normalement par Ca (2.07% en moyenne). Les paramètres de la maille, ainsi que le comportement thermique, sont caractéristiques d’une apatite-(CaOH) carbonatée de type A, contenant de l’eau moléculaire et du carbonate en tant que remplaçants de l’hydroxyle dans les tunnels structuraux. La multiplicité des bandes dans le spectre d’absorption en infrarouge (3&#9573 + 1&#9571 + 3&#9574 + 2&#9572) concorde avec une symétrie ponctuelle C6 de l’anion phosphate. La whitlockite obtenue après la décomposition thermique à 1000°C de l’apatite-(CaOH) contient du sulfate. Si authigène, l’apatite-(CaOH) de Cioclovina est issue des réactions entre le carbonate de calcium des coulées de “lait de lune” ou du socle de la grotte et les solutions phosphatées dérivées du guano, ayant la brushite ou des phases amorphes auxrayons X comme précurseurs.

International audience; The paper aims to give details on the phosphate association from the Mereşti Cave, Perşani Mountains, Romania. Ca-phosphates (i.e., hydroxylapatite, brushite and ardealite) are the main components of the guano deposit inside this cave. Associated minerals include gypsum, low quartz, 2M1 illite, interstratified kaolinite-illite, calcite and X-ray amorphous iron sesquioxides. Hydroxylapatite {[Ca9.804Mn0.004Mg0.067Fe2+0.054K0.002Na0.003](P5.934S0.066)O23.929(OH)2.071} has a = 9.434(3) Å, c = 6.868(3) Å and V = 529.7(3) Å3, Dx = 3.142 g/cm3, D = 3.14(1) g/cm3, ω = 1.647(1) and ε = 1.641(1). CO3 bands in the infrared absorption spectrum (ν3 = 1466 cm–1), ν3' = 1430 cm–1), ν2 = 872 cm–1) show that hydroxylapatite from Mereşti is carbonate-bearing. Brushite has the mean chemical-structural formula [Ca0.984Mn0.002Mg0.009Fe2+0.004K0.001Na0.001](HPO4)0.976(SO4)0.024 . 2H2O. Both unit cell [a = 5.812(5) Å, b = 15.169(5) Å, c = 6.239(4) Å and β = 116.35(13)°] and physical parameters [D = 2.32(1) g/cm3, α = 1.540(2), β = 1.546(2), γcalc = 1.551, for 2Vα = 86°) characterize a term close to stoichiometry. Ardealite has the mean chemical structural formula {[Ca1.992Mg0.004Fe2+ 0.002K0.001Na0.001](HPO4)1.021 (SO4)0.979 ˙ 4H2O}. Its mean unit-cell parameters are a = 5.718(3) Å, b = 30.998(24) Å, c = 6.248(5) Å and β = 117.17(5)˚, and the measured physical constants α = 1.529(2), β = 1.537(2), γ (calculated for 2Vα = 86°) =1.544, and D = 2.327(3) g/cm3. The textural relationships between the three calcium phosphates, observed by scanning electron microscopy and energy-dispersive electron microprobe analysis, suggests that their sequence of crystallization was from hydroxylapatite to brushite and fi- nally ardealite. All the three species clearly resulted from the reaction between the strongly acidic solutions derived from the guano mass and the cave floor or moon-milk flows.