Single crystals of calcite exhibiting a morphology of well-defined 8-armed stars, which evolved from original rhombohedral calcite crystals with their 8 points extending radially into eight arms, were produced by crystallization of CaCO3 in agarose gels.

Batch experiments, combined with in situ spectroscopic methods, are used to examine the coprecipitation of Cr(VI) with calcite, including partitioning behavior, site-specific distribution of Cr on the surface of calcite single crystals, and local coordination of Cr(VI) in the calcite structure. It is found that the concentration of Cr incorporated in calcite increases with increasing Cr concent...

Synthetic calcite (CaCO3) particles are found in a broad range of applications. The geometry of particles produced from limestone or precipitation are versatile but limited to basic shapes. The microalga Emiliania huxleyi produces micro-structured calcite platelets, called coccoliths. This article presents the results of an application-orientated study, which includes characteristic values also...

The application of stable isotopes in speleothem records requires an understanding of the extent to which speleothem calcite isotopic compositions refl ect the compositions of the cave waters from which they precipitate. To test for equilibrium precipitation, modern speleothem calcite was grown on glass plates, so that the carbon and oxygen isotope composition of the calcite and the water from ...

Chicken eggshell is a biomineral composed of 95% calcite calcium carbonate mineral and of 3.5% organic matrix proteins. The assembly of mineral and its structural organization is controlled by its organic matrix. In a recent study [1], we have used quantitative proteomic, bioinformatic and functional analyses to explore the distribution of 216 eggshell matrix proteins at four key stages of shel...

Ultrasound has revolutioned the care of women carring twins. First trimester evaluation is the best time to determine chorioniocity and amnioniocity in multiple gestations. First trimester diagnosis is based on the number of gestational sacs, amnions and yolk sacs. Growth rate in multiple multiple gestations during the fist and early second trimesters parallels the growth rate of singleton preg...

The oxygen isotopic compositions of calcite grains in four CM carbonaceous chondrites have been determined by NanoSIMS, and results reveal that aqueous solutions evolved in a similar manner between parent body regions with different intensities of aqueous alteration. Two types of calcite were identified in Murchison, Mighei, Cold Bokkeveld and LaPaz Icefield 031166 by differences in their petro...

We have investigated dissolution and surface reaction of calcite and aragonite in amino acid solutions of L-glutamic (L-glu) and L-aspartic acid (L-asp) at weak acidity of above pH 3. The surface reactions of calcite and aragonite were related with the dissolution. Calcite was dissolved in both solutions but the dissolution was limited by an adsorption of Ca-carboxylate salt. Aragonite was neit...

We report an interesting process whereby the formation of nanoparticle assemblies on and nanoporosities within calcite crystals is directed by an intrinsically disordered C-RING mollusk shell nacre protein, AP7. Under mineralization conditions, AP7 forms protein phases that direct the nucleation of ordered calcite nanoparticles via a repetitive protein phase deposition process onto calcite crys...