Olga V. Frank-Kamenetskaya

On the origin of anomalous birefringence in grandite garnets

Abstract The origin of anomalous birefringence of grossular-andradite (grandite) garnets from skarns in Mali and Russia was considered. The crystals had complex optical patterns which can be induced by superposition of two phenomena: mismatch compositional strain (stress birefringence) and growth ordering of atoms (growth dissymmetrization). Study of the crystals using several experimental techniques (optical microscopy, microprobe analysis, X-ray diffraction topography and X-ray single crystal diffraction) as well as calculations of anomalous birefringence has confirmed this hypothesis. Depending on the crystal composition and growth conditions, the relative magnitude of each phenomenon controls the various optical effects. As a result one can see two groups of crystals which are found to have fundamentally different anomalous optical properties: crystals with low (<0.001) and high (0.001-0.015) values of birefringence. The spatial distribution of birefringence within each group is different and this fact is related to different mechanisms causing optical anomalies: stress birefringence and growth dissymmetrization for these two groups, respectively.

The influence of amino acids on the formation of nanocrystalline hydroxyapatite

The influence of amino acids on the formation of particles of synthetic analogs of hydroxyapatites of renal calculi with different degrees of nonstoichiometry is investigated. It is demonstrated that the electrokinetic properties (the charge and the potential) and the dispersion composition of the synthesized hydroxyapatite sols depend on the Ca/P atomic ratio. The results obtained allow the assumption that, under the normal physiological conditions, free amino acids are natural inhibitors for the formation of renal calculi in the human organism.

Bioactive coatings based on nanodiamond-modified epoxy siloxane sols for stone materials

Using a sol-gel process, we have prepared bioactive organic-inorganic hybrid coatings based on epoxy siloxane sols modified with detonation nanodiamond. The microstructure of the coatings was studied by scanning electron microscopy. The coatings were tested—under both laboratory and urban conditions—for bioactivity against the mold fungi most frequently encountered in the air in large cities. The results suggest that such coatings are potentially attractive for protecting historic monuments from biodeterioration.

Weddellite from renal stones: Structure refinement and dependence of crystal chemical features on H2O content

Abstract The refinement of the structures of 17 weddellite crystals [Ca(C2O4)·(2+x)H2O, I4/m, a = 12.329-12.378 Å, c = 7.345-7.366 Å, V = 1117.8-1128.6 Å3], which were taken from the oxalic renal stones of the St. Petersburg (Russian Federation) citizens of both sexes aged from 24 to 65 years, has been carried out by the means of single-crystal X‑ray diffraction (R1 = 0.024-0.057). According to the results of the study, the amount of “zeolitic” water molecules (x) in the structure of weddellite varies from 0.13 to 0.37 pfu. A significant positive correlation between the amount of “zeolitic” water in the structure of weddellite and the closest interatomic distance between coordination water molecules in the large channels (OW1-OW1) was found as well as positive correlation between the value of the a parameter and the average distance of in Ca polyhedron. Obtained linear regression equation: x = 5.43a - 66.80, can be used for determination of the “zeolitic” water amount using the known unit-cell a parameter with mean-root-square error ±0.03 pfu. It was found that the x value for the crystals selected from the “mono-weddellite” stones (x = 0.13-0.24) are at the bottom of the range, thus we can assume that weddellite crystals with fewer “zeolitic” water amounts would be relatively stable. This work expands the knowledge of pathogenic crystal growth processes in living organisms and the development of the theory of oxalate stone formation in humans and animals, and may provide a building block for biomolecular technologies that approach the prevention and treatment of diseases associated with lithiasis.

On the complex zonality in grandite garnets and implications

Abstract The available data on compositional zoning in grossular-andradite (grandite) garnets occurring at different scales, mainly due to the variations of their Fe3+/Al ratios, and the hypotheses on the origin of this zoning are reviewed. Four zoned crystals of grandites showing different optical properties have been studied by means of X-ray diffraction. Optical and structural studies suggest three superimposed scales of Fe3+/Al zonality along [110]. The drastic change of the structural characteristics from sample to sample correlates with the change of their optical patterns. The superfine oscillatory zoning has been described in terms of irregular interstratified structures with a high degree of segregation. The self-affinity of zoning at different scales testify to the possible origin of the zonality due to the non-linear dynamics at the growth from. The wide variation of the layer compositions revealed by the modelling of the X-ray diffraction profiles seems to contradict the hypothesis of unmixing in grandite garnets.

Specific features of pathogenic mineral formation in the human body

Key relationships in pathogenic mineral formation within the human body were summarized. It was shown that pathogenic organomineral aggregates in human body are formed in complex multicomponent media containing organic and inorganic components. In the course of lithogenesis, the composition of biological fluid undergoes major changes. Phase formation in human urine and oral fluid in the initial stages leads to emergence of less thermodynamically stable phases, i.e., is kinetically controlled. Amino acids, as well as a number of inorganic impurities, are actively involved in crystallization of the main phases of renal calculi.

Decaying of the marble and limestone monuments in the urban environment. Case studies from Saint Petersburg, Russia

The results of a long-lasting research of sulphation process, which causes an essential deterioration of marble and limestone monuments in Saint Petersburg are reported. Based on a variety of field and analytical methods we can show that the decay process forming a gypsum-rich patina depends mainly on the local environment, the moisture accumulation, and is connected with the fissuring and porosity of the rock and the relief of a monument. Three main stages of gypsum-rich patina formation in the presence of microorganisms were revealed.

Thermodynamic and experimental modeling of the formation of major mineral phases of uroliths

Solubility diagrams have been calculated for the major phases of uroliths and their binary systems with a common cation or anion at 25°C. Phase-formation laws under the conditions of healthy human urea have been experimentally studied. The adequacy of the theoretical and experimental modeling to pathogenic mineralization in humans is analyzed. The applicability limits of the thermodynamic model have been refined.

Symmetry and crystal structure of biaxial elbaite-liddicoatite tourmaline from the Transbaikalia region, Russia

Abstract Optical anomalies and crystal structures have been studied for an elbaite-liddicoatite tourmaline specimen from the Malkhan pegmatite field (Transbaikalia region, Russia). The specimen is characterized by a complicated zoning and sector zoning distribution of anomalous biaxiality, with the axial angle 2V increasing from 3 up to 23° going from the first to the last growth zones of the most developed growth sector, o{022̅1}. The crystal structures of three samples cut out from different growth zones of that sector and characterized by the axial angles 11, 16, and 23° were refined in the trigonal space group R3m as well as in its monoclinic and triclinic subgroups Cm, R1, and P1, respectively (R = 0.019-0.039). The final choice of the low symmetry space group R1 is based on the analysis of the diffraction patterns and on the results of crystal structures refinements, which revealed ordered Al/Li distributions over the Y octahedral sites. The degree of order at Y sites correlates with the axial angle 2V, which implies a causal relationship. The Al/Li ordering reflects the geometrical differences of the octahedral sites with respect to the growth front orientation. The results obtained suggest that a growth dissymmetrization mechanism is the main reason for the observed cation ordering and optical anomalies.

Crystal structure and stability of Ni-rich synthetic tourmaline. Distribution of divalent transition-metal cations over octahedral positions

Abstract The crystal structure of synthetic Ni-rich tourmaline with a nickel content of 18.96 wt.% NiO (a = 15.890(2), c = 7.1815(8) Å) has been refined to R = 3.1% using single-crystal X-ray diffraction data. It has been shown that Ni is distributed not only over the Y, but also over the Z sites according to the ideal formula Na(Ni2+2 Al)(Al5Ni2+)(Si6O18)(BO3)3(OH)4. Based on bond valences and charge balance analysis it has been shown that this composition corresponds to the stable disordered member of the solid solution series NaAl3Al6(Si6O18)(BO3)3(O)3(OH) - NaNi2+3 Al6(Si6O18)(BO3)3(OH)4. Taking into consideration available structural data on Me2+ (Ni, Cu, Co, Fe, Mn)-rich tourmalines, cation-size mismatch and bond-valence calculations we assume that there are no structural constraints precluding occurrence of these cations in both octahedral sites. Divalent transitional metal-rich tourmalines have not been found in Nature probably due to the insufficient concentration of these elements in B-rich geological systems.