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International audience; Guano is a typical deposit found in caves derived from the excretions of bats and in minor cases of birds. These organic deposits decompose and form a series of acid fluids and gases that can interact with the minerals, sediments, and rocks present in the cave. Over sixty phosphates are known and described from caves, but guano decay also often leads to the formation of nitrates and sulfates. In this study twenty-two European caves were investigated for their guano-related secondary minerals. Using various analytical techniques, seventeen phosphates, along with one sulfate (gypsum), were recognized as secondary products of guano decay. Among those minerals, some are very rare and result from the interaction of guano leachates with clays, fluvial deposits, or pyrite. Some of these minerals are even found only in the studied caves (spheniscidite, robertsite). The most common minerals belong to the apatite group. The common mineral association present in fresh decaying guano is brushite-ardealite-gypsum, minerals that usually are not present in older deposits because of their higher solubility. Most minerals are in hydrated form because of the wet cave environment; however, some specific dry conditions may favor the presence of dehydrated minerals, such as berlinite, formed during guano combustion. Investigation on the acidity of guano piles shows pH values as low as 3.5 with an increase of acidity with age and depth. Finally, cave guano deposits should be better studied in the future because of their role in paleoenvironmental and paleoclimatic reconstructions and because it is important to better understand the origin of guano-related minerals, especially the phosphates and sulfates. Among all of the caves studied, Corona ’e sa Craba (Italy) and Domica-Baradla Cave (Slovakia-Hungary) are considered to be outstanding sites with respect to their phosphate mineralogy.

Over the past 15 years several expeditions by French, American and especially Italian cavers have unveiled over 50 caves in the Cordillera de la Sal (Atacama Desert, Northern Chile). Many of these caves contain a variety of speleothems and minerals, some of which have rarely been observed within karst systems. Most of the secondary deposits in these caves are composed of halite, but also other halide, carbonate, sulphate, nitrate, phosphate, and silicate minerals have been found. Among the sixteen cave mineral species recognized, atacamite, darapskite, blödite, leonite, anhydrite, and especially antarcticite are worth mentioning. In one of the samples an unknown Ca-Sr-bearing chloride mineral has also been discovered, but it has not been possible to carry out detailed mineralogical analyses. These often-rare minerals have formed in this region due to the very extreme hyperarid and salt-rich environment. This research reports the mineralogical results and proposes the genetical mechanisms leading to the formation of antarcticite, powdery anhydrite, and the paragenesis of the halite-darapskite-blödite. This study also shows that Atacama caves may be excellent analogues to study weathering processes and subsurface secondary minerals in hyperarid and hypersaline environments on Mars.

Karst in Sicily develops in both Messinian gypsum and Mesozoic or Tertiary limestone rocks. Caves are also found in the basalts of Mount Etna. Except for some rare cases, until recently most caves developed in limestone were considered to be of epigenetic origin. The discovery of gypsum in some of these caves, and especially detailed morphological studies, have allowed defining a hypogenic origin for a dozen of caves up to now. In some of these, the hypogenic evidences are very clear, while others remain in doubt because of the widespread presence of well-developed condensation-corrosion morphologies not necessarily related to hydrothermal fluids. This paper reports the present knowledge of hypogenic caves in the Island of Sicily.

Montecchio cave (Grosseto province, Tuscany, Italy) opens at 320 m asl, in a small outcrop of Jurassic limestone ( Calcare Massiccio Fm.), close to the Albegna river. This area is characterised by the presence of several thermal springs and the outcropping of travertine deposits at different altitudes. The Montecchio cave, with passage length development of over 1700 m, is characterised by the presence of several sub-horizontal passages and many medium- and small-scale morphologies indicative of sulphuric acid speleogenesis (SAS). The thermal aquifer is intercepted at a depth of about 100 m below the entrance: the water temperature exceeds 30 °C and sulphate content is over 1300 mg l − 1 . The cave hosts large gypsum deposits from 40 to 100 m below the entrance that are by-products of the reaction between sulphuric acid and the carbonate host rock. The lower part of the cave hosts over 1 m thick calcite cave raft deposits, which are evidence of long-standing, probably thermal, water in an evaporative environment related to significant air currents. Sulphur isotopes of gypsum have negative δ 34 S values (from − 28.3 to − 24.2‰), typical of SAS. Calcite cave rafts and speleogenetic gypsum both yield young U/Th ages varying from 68.5 ka to 2 ka BP, indicating a rapid phase of dewatering followed by gypsum precipitation in aerate environment. This fast water table lowering is related to a rapid incision of the nearby Albegna river, and was followed by a 20–30 m fluctuation of the thermal water table, as recorded in the calcite raft deposits and gypsum crusts.

Rossiantonite, ideally Al3(PO4)(SO4)2(OH)2(H2O)10·4H2O, triclinic (space group P 1), a = 10.3410(5), b = 10.9600(5), c = 11.1446(5) A, α = 86.985(2), β = 65.727(2), γ = 75.064(2)°, V = 1110.5(1) A3, Z = 2, is a new mineral from the Akopan-Dal Cin cave system in the Chimanta massif (Guyana Shield, Venezuela). The mineral occurs as small (≤0.15 mm) and transparent crystals in a white to slightly pink fine-grained sand, filling spaces between boulders of weathered quartz sandstone. Associated phases are gypsum, sanjuanite, rare alunite, quartz and micro-spherules of amorphous silica. Rossiantonite is colorless with a white streak and vitreous luster. The mineral is brittle with irregular to sub-conchoidal fracture and it shows a poorly developed cleavage. Rossiantonite is biaxial and not pleochroic, with mean refractive index of 1.504. The calculated density is 1.958 g/cm3. Electron microprobe analyses, with H2O measured by thermogravimetric analysis, provided the following empirical formula based on 28 O apfu: Al2.96Fe0.03P1.01S2H30.02O28. The five strongest lines in the X-ray powder diffraction pattern, expressed as d (A), I , ( hkl ) are: 4.647, 100, (210); 9.12, 56, (100); 4.006, 53, (220); 8.02, 40, (110); 7.12, 33, (011). The crystal structure, refined using 3550 unique reflections to R = 0.0292, is built of PO4 and Al O6 polyhedral rings, creating complex chains parallel b by sharing the OH-OH edge belonging to the Al(3) polyhedron. Three symmetrically independent Al sites can be identified, namely: Al(1), Al(2), and Al(3). Tetrahedral sites, occupied by P, share all their apexes with AlO6 octahedra. Unshared octahedral apexes are occupied by water molecules. Four additional water molecules are placed in between the previously identified chains. Two oxygen tetrahedra, occupied by S atoms, are connected along the chains by means of weak hydrogen bonding. The rossiantonite structure shows similarities with minerals belonging to the sanjuanite-destinezite group.

The thermally induced structural modifications of the natural zeolite gottardiite ((Na 0.78 K 0.24 Mg 3.51 Ca 4.11 Sr 0.06 Ba 0.05 )(Fe 0.14 Al 17.47 Si 118.70 O 272 )·92.33H 2 O, a = 13.631(1), b = 25.047(3) and c = 22.586(3) A, V = 7711(1) A 3 , s.g. Cmca , framework type NES) were studied in the temperature range 308–1203 K in a temperature-resolved X-ray powder diffraction experiment, using synchrotron radiation. The unit cell parameters were refined in the whole temperature range, while structural refinements were performed approximately every 100 K, at 308, 371, 475, 580, 674, 779, 873, and 978 K. No signs of phase transitions were observed in the whole investigated T -range and up to the highest temperature the material does not undergo amorphization. Gottardiite shows a high thermal stability, as a consequence of the high Si content, and an extremely rigid structure with a substantial absence of cell volume change. The framework deformation induced by dehydration involves only a slight distortion of the 10-ring and 12-ring channels running in the a and b directions. From room temperature to 580 K gottardiite looses water quite slowly and regularly. The main water loss is observed in the temperature range 580–779 K. Above this temperature gottardiite again dehydrates slowly, and at 978 K some water molecules even remain.

The crystal structure of direnzoite, a new natural zeolite found in the cavities of a xenolitic rock from the Massif Central (France) is reported. Apparently, direnzoite was formed throughout a process of hydrothermal crystallization within the vugs of a highly porphyric basalt. The determination of the crystal structure of this new zeolite was at the limits of the existing experimental techniques because of the paucity of available specimen, mainly composed of three tiny aggregates of fibrous microcrystals. The structure of direnzoite, solved by powder methods, was shown to be the K-dominant equivalent of the synthetic zeolite ECR-1 with a framework composed of layers of mordenite (MOR) and mazzite (MAZ) connected in a regular 1:1 stacking sequence with assigned framework topology EON. The chemical composition of direnzoite determined from the structure refinement is (Na0.94K6.62Mg1.42 Ca2.24)(Si, Al)60O120·36.8H2O. The unit cell determined from the Rietveld structure refinement is a = 7.57887(18) A, b = 18.20098(57) A, c = 26.15387(83) A, and the space group is Pmmn . Six extra-framework sites and 14 water molecules were identified within the zeolite micropores. Three extra-framework sites are occupied by K+ ions. The others are occupied by Na+, Ca++, and Mg++. Although direnzoite and ECR-1 share the same framework, the distribution of their extra-framework cations is rather different. In direnzoite, there are no equivalent positions to C1, C2, and C4 positions found in ECR-1. Only sites C3 and C3b correspond respectively to K3 and Ca in direnzoite. In direnzoite, K1, K2, and Na correspond to water molecules sites (H2O1, H2O11, and H2O8, respectively) in ECR-1.

Objective To assess the burden and chemical and mineralogical composition of stent coating at both stent ends, with evaluation of associated risk factors. Materials and Methods A total of 40 consecutive patients submitted to ureteral-stent removal were considered. Stents were previously positioned for both urolithiasis and during the management of other urologic diseases and/or procedures. Mean indwelling time was 59.2 ± 7.5 days. Analytical procedures Encrustations were submitted to chemical-mineralogical analysis as well as to their quantification. Quantification was achieved by measuring the weight of stent fragments before and after oxidative acid treatment to dissolve the deposited (both organic and inorganic) material. The analytical solution obtained by acid attack was used to acquire information on calcium and magnesium content with atomic-absorption spectroscopy. X-ray diffraction was used to determine the mineralogy of encrustations for a group of stent samples characterized by relatively high amounts of deposited material. Results The composition of encrustations at the proximal coil reflected the composition of stones in patients with urolithiasis. Whewellite was the more common encrustant. In a regression model, the variable mostly related to the burden of proximal encrustation was urolithiasis ( P = .04), especially in frequent stone formers. At the distal coil, higher degrees of encrustation were related to urinary tract infection ( P = .012) and patient's aging ( P = .05), thus suggesting a possible association with a bladder outlet dysfunction. Conclusion The present study highlighted some variables related to stent encrustation and seems to be the first one analyzing separately the two coils. Our outcomes suggest that the so-obtained risk factors have to be considered when positioning a ureteral stent.

A new occurrence of katoite (Ca2.95Fe0.03A12.03(SiO4)1.12(OH)7.51; a = 12.286) found near Dunabogdany (Hungary), along with its structural refinement is reported here. The crystal-chemical data, the physical properties, and the structure refinement of this new member of the Ca3Al2(SiO4)3-Ca3Al2(O4H4)3 series indicate the presence of about 37% grossular. The positional disorder of the oxygen atom, a peculiar feature of the hydrogarnet structure, is described here in terms of both anisotropy along the d-O vector, and presence of two distinct oxygen sites (unsplit- and split-O models, respectively). The hydrogen atom was localised for both models in the difference Fourier map. The structural features of the katoite from Dunabogdany are compared with those of other hydrogrossulars and with the two end-members “anhydrous” grossular, and Si-free katoite. The results of the unsplit-O model refinement confirm the increase of the tetrahedron volume with the substitution of Si by 4H+. The geometry of the coordination polyhedra in the two configurations resulting from the split-O model are also discussed. This second model better describes from the crystallochemical point of view the substitution of Si4+ with 4H+ in the tetrahedra. However, the tetrahedra of the two dimensions are randomly distributed in the unit cell and hence domains of the two end-member configurations are not expected in katoite structure. This conclusion is also strengthened by the TEM study of katoite from Dunabogdany.**

Kenya is one of the few countries in which karst cavities are scarce with respect to volcanic ones, which are widespread throughout the whole country. The great variability in lava composition allowed the evolution of very different cavities, some of which are amongst the largest lava tubes of the world. As normal for such a kind of cave, the hosted speleothems and cave minerals are scarce but important from the minerogenetic point of view. Anyway up to present no specific mineralogical research have been carried out therein. During the 8th International Symposium on Volcanospeleology, held in Nairobi in February 1998, some of the most important volcanic caves of Kenya have been visited and their speleothems and/or chemical deposits sampled: most of them were related to thick guano deposits once present inside these cavities. Speleothems mainly consisted of opal or gypsum, while the deposits related to guano often resulted in a mixture of sulphates and phosphates. The analyses confirmed the great variability in the minerogenetic mechanisms active inside the volcanic caves, which consequently allow the evolution of several different minerals even if the total amount of chemical deposit is scarce. Among the observed minerals kogarkoite, phillipsite and hydroxyapophyllite, must be cited because they are new cave minerals not only for the lava tubes of Kenya, but also for the world cave environment. The achieved results are compared with the available random data from previous literature in order to allow an updated overview on the secondary cave minerals of Kenya.

The paper presents a detailed study demonstrating the hypogenic origin of the Corona 'e Sa Craba quartzite cave in SW Sardinia (Italy). Although the quartzite host-rock of this cave derived from silicification of Cambrian dolostones and dissolution of carbonate remnants could have had a role in the speleogenesis, detailed morphologic and petrographic investigation revealed clear evidence of quartz dissolution without signs of mechanical erosion by running waters. Thin section microscopy and scanning electron microscope (SEM) images show pervasive dissolution morphologies, such as pits and notches on quartz crystals causing the deep arenization of the cave walls, suggesting that the dissolution of quartz had a primary role in the formation of the void. The study of secondary cave minerals and the sulfur isotopic composition of sulfates and sulfides, coupled with data on fluid inclusions, allowed reconstruction of the peculiar speleogenetic history of this hypogenic hydrothermal quartzite cave. The cave formed by reduced hydrothermal fluids, probably under basic neutral pH in phreatic conditions. The presence of abundant cations of Ba2+ in reduced Cl-rich fluids enhanced the quartz dissolution rate, allowing the formation of the voids in deep settings. During the Late Oligocene uplift of the area, the hydrothermal fluids in the cave reached oxygen-rich conditions, thus a minerogenetic phase started with the deposition of barite when the temperature of the fluid was

To verify chromium enrichment of the muscovite layer, a crystal chemical and XANES study on chromium-containing muscovite crystals from the South Island of New Zealand was carried out. The crystals studied differ from those of end-member muscovite in that they display variable levels of octahedral substitutions and homovalent and heterovalent substitution of K in interlayer sites. Single-crystal X-ray diffraction data were collected for three crystals in the space group C 2/ c to an agreement factor (R obs ) from 0.025 to 0.033. Tetrahedral cation disorder was found for each sample and the values of mean bond length for both tetrahedra do not depart significantly from that of the end-member muscovite-2 M 1 . Electron density at the M2 site is greater than that required for the ideal muscovite-2 M 1 structure, and a small excess of electron density is found for two crystals in M1. As the octahedral substitution of larger cations for Al increases in the octahedral sites, the match between tetrahedral and octahedral sheets improves and tetrahedral rotation angle, α, decreases. XANES spectra at the Cr K-edge in these chromium-containing muscovite samples exhibit octahedral symmetry. Moreover, a careful analysis of the pre-edge region shows at least two features. A qualitative fitting procedure of the pre-edge region indicates that no more than 0.5% of total Cr(III), if any, may occupy the tetrahedral site.

Hyodeoxycholic acid (HDCA) isa 6-α dihydroxylated natural bile acid capable ofpreventing gallstone formation by reducing the bilecholesterol saturation. However, any attempt to enrichthe bile acid pool with HDCA have failed owing to thepoor solubility of the molecule. To resolve thebioavailability problems, the complexation of HDCAinto the HPβCD cavity was studied in solution(solubility methods, 13C- and 1H-NMRspectroscopy and circular dichroism) and in the solidstate (IR spectroscopy, X-ray diffractometry andthermal analysis). According to the results, the HDCAinclusion took place with 1 : 1 stoichiometry. Theinfluence of different preparation methods of thesolid complex was evaluated for its potential use inappropriate pharmaceutical formulations to improve thebioavailability of HDCA.

SUMMARYWe carried out a comparative cytogenetic study on gall-forming generations of Tetraneura nigriabdominalis and Tetraneura ulmi using NOR and C-banding followed by Giemsa, Chromomycin A3 (CMA3) and DAPI staining reactions in order to improve our knowledge of these species and better define their identification. In both species, C-banding revealed that heterochromatin was not equilocated on each chromosome. Moreover, in T. nigriabdominalis the C-banding technique identified B chromosomes. The different response to the CMA3 and DAPI staining reactions after C-banding points out heterogeneity of the heterochromatic DNA composition in both species. Moreover, both CMA3 and silver staining revealed heteromorphism of NORs.

Well-crystallized euhedral crystals of aluminian lizardite-2H 2 (Mg (sub 2.35) Fe (super 2+) (sub 0.06) Fe (super 3+) (sub 0.07) Al (sub 0.52) ) (Si (sub 1.41) Al (sub 0.59) )O (sub 5.00) (OH) (sub 4.00) were found near Schio (Vicenza, Italy). To gain insight into the role of a high Al content lizardite, chemical analyses and single-crystal X-ray data collection were conducted. Structure refinement, completed in space group P6 3 (agreement factor R = 0.034), gives mean T-O values of 1.654 Aa and 1.664 Aa for T1 and T2 sites, respectively. The ditrigonal distortion of the six-membered tetrahedral ring is positive (alpha = +9.7 degrees ), as expected for the 2H 2 polytype. The octahedral site has a mean bond length similar to that of the Mg-rich octahedra of amesite and distortion parameters similar to those of Al-rich octahedra.

A Ba-rich celestine (Sr0.87Ba0.13SO4) filling cavities of volcanoclastic rocks from Montecchio Maggiore (Vicenza, Italy) was studied. The role of the Ba content in the mineral was determined using X-ray powder data, single crystal X-ray refinement, thermal and chemical analyses. The unit cell parameters (obtained by single crystal diffraction) are a = 8.408, b = 5.372, c = 6.897 Å, and the refinement in the space group Pnma (Z = 4) gives the final R value of 0.039. The average (Sr,Ba)-oxygen bond length is 2.842 Å and agrees with an occupancy of Sr 87% and Ba 13%. Individual bond lengths (Sr,Ba)-O and bond strength calculations confirm that all twelve interactions are significant and define an irregular array around the cation.

We investigated the crystal-chemical features of six crystals of lizardite-1 T sampled in four outcrops of ophiolite, at Pompeano, Sassomorello, Varana, and Santa Scolastica, in the Modena Apennines, Italy. In spite of the extensive contributions already present in the literature, this is the first study dealing with lizardite from the Modena ophiolites. As is clear from one of our samples, the whole-rock composition affects the composition of lizardite, which makes it susceptible to overprinting by later metasomatic events. In our study, we paid particular attention to the effects of VI Mg −1 VI Fe 2+ and of IV Si −1 IV Al VI (Mg, Mn, Fe) 2+ −1 VI (Al, Cr, Fe) 3+ exchange mechanisms on the structure. Our results suggest that VI Mg −1 VI Fe 2+ substitution induces an increase in the M –O4 length in octahedra and a decrease in the octahedral-site distortion. Both these effects are also observed to influence the unit-cell parameter c . The effect of the IV Si −1 IV Al VI (Mg, Mn, Fe) 2+ −1 VI (Al, Cr, Fe) 3+ substitution is to decrease the M –O1 distance and concomitantly, to increase the T –O1 distance.

This paper presents the results of a study on the speleogene­sis and the speleothems and secondary mineralisations of the Santa Barbara Cave System in the Iglesiente Mining District (South-West Sardinia, Cagliari). This cave system, hosted in Cambrian carbonate rocks, has a very long geological history and its main voids have formed in hypogenic conditions. Nine speleogenetic phases can be recognised ranging in age between Cambrian and Holocene. Optical microscope and diffracto­metric analysis of active flowstone deposits have shown them being composed of alternating calcite and aragonite layers. The textural and chemical characteristics of these layers, obtained by SEM and EDAXanalysis, suggest them to be related to varia­tions in the depositional environment inside the cave, whichin turn are probably correlated to external climatic oscillations.

In June 1978, during a field trip to Massif Central (France), Professors Ermanno Galli and Glauco Gottardi collected a piece of rock (xenolith) of about 20 cm diameter, plenty of cavities filled with crystals of secondary minerals. Exactly 30 years later, it is possible to claim that one of those was a new zeolite species. The structure of this natural zeolite, called direnzoite, and its synthetic counterpart ECR-1 were both solved using synchrotron powder diffraction. As a matter of fact, the structure of ECR-1 was used for the structure solution of direnzoite, the latest discovered natural zeolite. The two structures are distinguished by a 1:1 polysomatic sequence of mordenite (MOR) and mazzite (MAZ) layers. This paper evaluates the differences of the two crystal structures in terms of framework attributes, extraframework cation distribution and relationship with the framework, and water molecules.

The Cueva de las Velas is the last cave unveiled at -290 level within the Naica Mine; the cavity has been intercepted by a mine gallery at the beginning of 2005. One of its peculiarities is the widespread thick deposits of diagenetic minerals deposited over the cave walls before the beginning of the evolution of the giant gypsum crystals. These deposits consist of complex, often scarcely crystalline iron-manganese-lead oxides-hydroxides, but carbonates, sulphates and silicates are also present. Other minerals, mainly sulphates, started developing just after this area of the mine was dewatered some 20 years ago. Presently 17 different minerals have been observed, 5 of which (orientite, starkeyite, szmolnokite, szmikite and woodruffite) are completely new for the cavern environment. The study of these minerals, together with the presence of a completely new type of gypsum crystals, allowed to improve the knowledge on the speleogenetic evolution of this cave, which seems to be by far more complex than that of the other cavity of the -290 level.Its complexity is reflected by the activity of a larger number of different speleogenetic mechanisms. Among them are worth of mention the thermal corrosion/dissolution, the anhydrite-gypsum disequilibrium, the acid aggression, and the capillary migration and evaporation.

Tschernichite, a very rare pentasil zeolite, is the natural aluminum-rich analog of zeolite beta, a large pore aluminosilicate, the peculiar structure and acidity of which makes it one of the most important acid catalysts. Tschernichite, like zeolite beta, is a disordered structure consisting of two distinct polytypes with monoclinic and tetragonal symmetry, respectively. The monoclinic polytype crystallizes in the C2/c space group, with cell parameters a = 17.982(1), b = 17.985(1), c = 14.619(1) A, β = 114.33 (1)°, and V = 4308 A3 at 25 °C, and its structure is characterized by a three-dimensional channel system of 12-membered rings of tetrahedra. The dehydration process of the monoclinic polytype |Na0.8K0.3Mg0.4Ca8.0(H20)67| [Al18.0Si46.0O128]-BEA was studied by single-crystal X-ray data diffraction collected at room temperature, at 80, 150, and 250 °C in a hot nitrogen stream. During the dehydration process, the variation of the unit-cell volume was always less than 1.3%. In room conditions, monoclinic...

Mazzite-Na, Na 8 Al 8 Si 2 8 O 7 2 .30H 2 O, is a new zeolite mineral species occurring in basalt at the bottom of the open pit of the U.S. Borax mine at Boron, California. It crystallizes as white, very thin, flexible fibers up to 2 mm in length, and commonly fills small cavities as satiny mats. The luster is vitreous, and the streak is white. The fineness of the fibers precludes the determination of the hardness and the observation of any cleavage. The observed and calculated densities are 2.16 and 2.18 g/cm 3 , respectively. The mineral is uniaxial positive with n e = 1.472(3) and n ω = 1.471(3). Electronmicroprobe analyses yielded (in wt%) SiO 2 57.65, Al 2 O 3 14.35, Fe 2 O 3 0.65, MgO 0.22, CaO 0.18, BaO 0.14, Na 2 O 8.07, K 2 O 0.03, and H 2 O 18.70 (TG analysis), which gives the empirical cell contents (Na 7 . 5 2 K 0 . 0 2 Mg 0 . 1 6 Ca 0 . 0 9 Ba 0 . 0 3 )[Fe 0 . 2 4 Al 8 . 1 3 Si 2 7 . 7 1 O 7 2 ].29.98H 2 O. Mazzite-Na is hexagonal, P6 3 /mmc, a = 18.2343(7), c = 7.6371(2) A, Z = 1. The strongest seven measured X-ray lines [d in A(I)(hkl)] are: 9.08(100)(110), 6.86(70)(101), 5.95(70)(210), 4.681(40)(211), 3.787(80)(002), 3.511(40)(112), and 3.150(70)(500). The framework consists of columns of gmelinite cages parallel to c, cross-linked to form two types of channels; one has an elliptical 8-ring cross section and the other has a circular 12-ring cross section. The extra-framework Na cations are located at three different sites. NaI is at the center of the 6-ring between adjacent gmelinite cages and is coordinated by six framework oxygen atoms and two H 2 O molecules. Nail lies on the centerline of the 8-ring channel and is coordinated by four framework oxygen atoms and two H 2 O molecules. NaIII occupies sites along the walls of the 12-ring channel and is coordinated with two framework oxygen atom and four H 2 O molecules. With the naming of this mineral for its Na dominant composition the original mineral is renamed mazzite-Mg, and the name mazzite is raised to series status.

The discovery of a new natural zeolite phase is a rare event since only less than one hundred natural zeolites are known to date. We have been recently involved in a research project aimed at the investigation of a microscopic aggregate coming from the Massif Central (France) that appears to be a new zeolite species. The sample was collected more than 30 years ago by Professors Gottardi and Galli and since then, many unsuccessful attempts have been made to disclose the crystal chemistry of this new species. The quantity of available material is very limited, and single crystals are not available. For this reason, structure determination from powder diffraction data is attempted. This work presents the results of preliminary chemical, microscopy and mineralogical characterization of this apparently unknown mineral, mainly using X-ray powder diffraction. All data point to a new zeolite species and the results will be hopefully integrated in the future with the crystal structure solution by the powder methods.

V Savdski Arabiji je bilo raziskanih in izmerjenih vec velikih vulkanskih jam v razlicnih poljih lave. Ena najvecjih je Ghar Al Hibashi na polju lave Harrat Buqum-Nawasif. To je v glavnem raven rov (400 m dolg in 15 m sirok), dostopen skozi majhno brezno, ki se odpira v stranskem rovu. Jama je dolgo služila za skrivalisce netopirjem, hijenam, volkovom in lisicam. Zaradi tega je dno jame, deloma iz debelih plasti nesprijetega peska, prekrito s stevilnimi kostmi in koproliti ter razmeroma velikimi kupi gvana. Nekateri so se bili vneli, zaradi cesar so deloma zgorele tudi na njih ležece kosti. Edine prave kapnike predstavlja nekaj majhnih, rumenih in prosojnih stalaktitov. Tekom treh odprav 2003 je bilo iz jame vzetih nekaj sekundarnih kemicnih odkladnin za mineraloske preiskave. Kljub majhnemu stevilu vzorcev je bilo do sedaj zaznanih vsaj 19 razlicnih mineralov, najvec takih, ki so povezani z biogeno mineralizacijo kosti in gvana. Trije od teh, pyrocoproite, pyrophosphite in arnhemite, so izredno redke organske spojine, izkljucno vezane na goreci gvano. Do danes so bili ti minerali znani le iz nekaj jam v Afriki. Zahvaljujoc tem odkritjem ni jama Hibashi le najpomembnejsa vulkanska jama v Savdski Arabiji, ampak tudi tamkajsnje dalec najbogatejse mineralosko nahajalisce. Zato te raziskave, ki se zdalec niso koncane, potrjujejo novejse domneve, da so v jamskem okolju prav vulkanske jame najprimernejse za razvoj razlicnih mineralogenih mehanizmov. Several large lava tubes have been explored and mapped in different lava fields around the Saudi Arabia. One of the largest is Ghar Al Hibashi, located in the Harrat Buqum-Nawasif lava field. It mainly consists of a huge rectilinear gallery (over 400 m long and 15 m wide) the access to which is through a small vertical pit reaching a side corridor. The cave was long used as a shelter for bats, hyenas, wolves and foxes. Therefore the entire cave floor, consisting of locally thick uncemented sand, is scattered with a great amount of bones and coprolites, while some rather large guano deposits are also found. Some of these guano deposits caught fire, which partially burnt the bones overlaying them as well. The only true speleothems consist of a few small yellow translucent stalactites. During three expeditions in 2003, a few samples of secondary chemical deposits were collected inside this lava tube to be analysed from the mineralogical point of view. Despite the scarcity of these samples, at least 19 different minerals have already been detected, most of which are related to the biogenic mineralization of bones and guano deposits. Three of them, pyrocoproite, pyrophosphite and arnhemite are extremely rare organic compounds strictly related to the guano combustion, which have been observed until now only in a few caves in Africa. Thanks to these findings Hibashi lava tube is not only the most important volcanic cave of Saudi Arabia but also by far the richest mineralogical shelter of the country. Therefore this research, which is far from coming to an end, confirms the recently advanced opinion that amongst the different cave environments, volcanic cavities are very favourable for the development of different minerogenetic mechanisms.

The tetragonal and monoclinic polytypes of tschernichite (the natural counterpart of zeolite beta) from Mt. Adamson (Antarctica) were isolated and studied by single-crystal X-ray diffraction using a diffractometer equipped with a CCD detector. Diffraction patterns were interpreted with the help of the OD theory, and synthetic precession images allowed us to overcome ambiguities regarding the symmetry assignment. The two crystalline phases isolated are characterized as two MDO polytypes, tetragonal and monoclinic with different crystal sizes (small and large crystals, respectively), morphologies (single tetragonal dipyramids and radiating hemispherical groups, respectively), and chemistries (high and low Si/Al ratio, respectively). Both refined structures showed regular T-O distances (in the range 1.56-1.68 A), and extraframework ions spreading over a large number of sites with low occupancy. Many independent sites were identified in both polytypes: in the monoclinic type three sites are occupied by Ca, whereas in the tetragonal three are occupied by C a and one by Mg. The location and coordination of the site with the highest Ca occupancy in the monoclinic polytype were satisfactorily reproduced by potential energy calculations.

Summary In the course of a systematic investigation of zeolites from Northern Victoria Land, Antarctica, a large number of zeolitic species was identified in the Jurassic Ferrar Dolerites of Mt. Adamson. Noteworthy was the presence of three new zeolites: gottardiite, the natural counterpart of the synthetic NU-87, terranovaite, and mutinaite, the analogue of ZSM-5, as well as the two very rare zeolites tschernichite the counterpart of zeolite beta, and boggsite. The chemical and crystallographic properties of these natural materials were compared with those of their synthetic analogues. The tetragonal and monoclinic polymorphic phases, which differ by crystal size, morphology and chemistry. The occurrence of these natural zeolites demonstrates that the chemical existence field of their synthetic counterparts is larger than that argued up to now, and that their synthesis can be obtained in the absence of an organic template.

We describe the crystal structure of the high-silica zeolite mutinaite, recently found at Mt. Adamson (Northern Victoria Land, Antarctica). Mutinaite is the natural counterpart of the synthetic zeolite ZSM-5. The new mineral, (Na 2.76 K 0.11 Mg 0.21 Ca 3.78 ) (Al 11.20 Si 84.91 ) · 6O H 2 O H 2 O, is orthorhombic, space group Pnma, with a = 20.201(2), b = 19.991(2), and c = 13.469(2) A. A single-crystal X-ray diffraction experiment was performed at the synchrotron radiation source ESRF (Grenoble). No Si-Al order in the framework has been detected. Large distances between ions in the channels and framework oxygens suggest weak interactions between the framework and extraframework species.

The paper reports the occurrence and the crystallochemical data of willhendersonite from the breccia ridge of a melilitite plug at Colle Fabbri, Terni, Italy. The chemical data point to great chemical variability, ranging from the composition of the holotype sample (CaKAl 3 Si 3 O 12 : 5 H 2 O) through intermediate compositions, to a Ca-pure term, and so they call for a chemical redefinition of the zeolite. The structural refinement of a Ca-pure willhendersonite single crystal exibits the same space group and Si/Al ordering as the holotype willhendersonite, but it displays significant differences in the distribution of the extraframework species. These structural features are discussed in the light of a comparison with the structures of the holotype willhendersonite and natural and exchanged chabazites.

The crystal structure of a natural offretite from Poia Creek, Adamello, Italy (schematic formula KCaMgAl 5 Si 13 O 36 :17 H 2 O) has been refined to a residual wR of 0.038. The offretite framework can be described by a sequence AABAAB … of 6-membered rings of tetrahedra. The (Si,Al) distribution (29% of AI in T1 and 37% of AI in T2) is consistent with the disorder found in tetrahedral sites for ail zeolites describable by sequences of 6-rings. K is at the center of the cancrinite cage and is coordinated to 6 framework oxygen atoms. Mg, placed at the center of the gmelinite cage, is coordinated to 6 water molecules; 4 of these are disordered on 9 possible positions relative to two sites with multiplicity 6 and 3, respectively. Ca atoms alternately occupy two sites near each other, at the center of the wide channel parallel to parameter c, and are octahedrally coordinated to the same water molecules. The strong differences in the T−O distances found between hydrated and dehydrated offretite are here explained in terms of interactions between extraframe-work ions and framework oxygens.

The crystal structure of the zeolite stellerite has been studied by X-ray methods : space group Fmmm with a = 13.599, b = 18.222, c = 17.863 (Å). The framework of stellerite is topologically the same as stilbite ; its content of exchangeable cations allows the highest symmetry compatible with the framework. An explanation is given for the lower, monoclinic, symmetry of the structure of stilbite., La structure cristalline de la zéolite « stellerite » a été étudiée par les méthodes de diffraction des rayons X : le groupe spatial est Fmmm avec a = 13, 599, b = 18,222, c = 17,863 (Å). La charpente de la stellerite est identique à celle de la stilbite ; son contenu en ions échangeables permet la symétrie la plus haute compatible avec la charpente. On explique en outre la symétrie inférieure rencontrée dans la stilbite monoclinique., Galli Ermanno, Alberti Alberto. The crystal structure of stellerite. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 98, 1, 1975. pp. 11-18.

The refinement of the crystal structure of Theigarhorn epistilbite showed the presence of two tetrahedral configurations, as in Elba dachiardite. These two configurations, obtained by the rotation of two tetrahedra around one edge, have both C2 symmetry, with different frequency (82% and 18% respectively), thus the resulting space group is C2. The presence of these two acentric domains is interpreted as a tendency to avoid the T 0 T angle of 1800 present in the topological symmetry C2/m of epistilbite. The amount of AI, obtained from the T 0 mean distance, has been corrected by a method which takes into account the influence of T 0 T angles on the measured T 0 distance, and resulted in good accordance with Al content from the chemical analysis. A remarkable degree of ordering in the Si/AI distribution has been found. Two extraframework cation and six water molecule sites have been located. Both cation sites have a square antiprism coordination; these polyhedra form clusters of four antiprisms, which are linked together as in a chessboard.

Crystal structures of natural and hydrated Na, Ca, Sr and K-exchanged chabazite from Keller (Germany) were refined at room temperature in the R 3 m space group. The most probable distribution of ions indicates the presence of four cation sites; one at the centre of the hexagonal prism, two in the large cage along the [111] diagonal, and the fourth near the 8-ring window which is split into two sites close to each other in the monovalent exchanged forms. The site at the centre of the D 6 R is empty in the Na and K-exchanged chabazites. In this last form one of the two sites along [111] is also empty. Water molecules are spread over a large number of sites, one with 100% occupancy, at the centre of the 8-ring window, the others, normally with low occupancy, inside the large cage. Occupancies of both cation and water molecule sites vary greatly in the different forms.

The crystal structure of the zeolite barrerite, [(Ca₁.₇ Mg₀.₃ Na₁₀.₉ K₂.₁) (Al₁₆.₄Si₅₅.₄) O₁₄₄] • 51.6H₂O, has been studied by X-ray methods : space group Amma with a = 13.643 (2), b = 18.200 (3), c = 17.842 (3) Å. The framework of barrerite is topologically identical to that of stilbite and stellerite. The lowering of the symmetry from Fmmm of stellerite to Amma of barrerite is due to the presence of cations in sites that are vacant in both stellerite and stilbite and which impose rotational displacements within the framework around the screw axes parallel to the a axis., La structure cristalline de la zéolite barrérite [(Ca₁,₇ Mg₀,₃ Na₁₀,₉ K₂,₁) (Al₁₆,₄Si₅₅,₄) O₁₄₄] • 51,6H₂O a été étudiée au moyen des rayons X : le groupe spatial est Amma avec a = 13,643 (2), b = 18,200 (3), c = 17,842 (3) Å. La charpente de la barrérite est identique à celles de la stilbite et de la stellérite. L'abaissement de la symétrie du groupe spatial Fmmm de la stellerite au groupe spatial Amma de la barrérite est une conséquence de la présence, dans des sites vacants, de cations soumis à des déplacements induits par des axes hélicoïdaux parallèles à a., Galli Ermanno, Alberti Alberto. The crystal structure of barrerite. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 98, 6, 1975. pp. 331-340.

Phillipsite occurs as clear transparent spheroids, colourless to yellow to reddish-orange in colour, in the vugs of a basalt at Saint-Jean-le-Centenaire, Ardèche, France. The fibrous radial nature of the spheroids can be observed under the microscope only between crossed polars. It is Si-richer than normal hydrothermal (i.e. occurring in vugs of massive rocks) phillipsites. The powder pattern lacks all those peaks which make the distinction between phillipsite and merlinoite possible. The peak broadening in the powder pattern indicates a crystallite size around 350 Å. On the whole, this anomalous zeolite is more similar to phillipsite than to merlinoite and, in detail, its features are near those of some sedimentary and some synthetic phillipsites., La phillipsite se présente en sphérules transparents rouge orange, parfois aussi jaunes ou incolores, dans les cavités du basalte près de Saint-Jean-le-Centenaire, Ardèche. On ne peut observer la nature fibroradiée des sphérules qu'au microscope entre nicols croisés. Ces cristaux sont plus riches en Si que la plupart des phillipsites hydrothermales (c'est-à-dire de celles présentes dans les cavités des roches massives). Sur le diagramme de poudre, les raies qui permettent de distinguer la phillipsite de la merlinoite sont absentes. D'après la largeur des raies du diagramme de poudre, on peut déduire que la taille moyenne des cristallites est à peu près de 350 Å. On peut dire que la zéolite anormale étudiée est plus semblable à la phillipsite qu'à la merlinoite et, en particulier, ses caractéristiques sont voisines de celles de quelques phillipsites sédimentaires et synthétiques., Passaglia Elio, Galli Ermanno, Gottardi Glauco, Vezzalini Giovanna. An anomalous phillipsite from Saint-Jean-le-Centenaire, Ardèche. In: Bulletin de Minéralogie, volume 108, 5, 1985. pp. 719-724.