Prismatic Calcite Research Articles

Poorly crystallized hydroxyapatite and calcium silicate hydrate composites: Synthesis, characterization and soaking in simulated body fluid

Development of the composites based on substances with a high bioactivity potential is of current interest to medical materials science because composites' properties can be modified by varying the components ratios. Weakly crystallized calcium phosphates and calcium silicate hydrates, possessing higher chemical reactivity than their crystalline forms, are promising salts to be studied as biomaterials' constituents. In this study, precipitation from aqueous solutions was employed to obtain apatite and calcium silicate hydrate composites. Synthesized solids were examined without high-temperature thermal pretreatment using X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), laser diffraction, physical adsorption (BET method) and thermogravimetric analysis coupled with the mass spectrometry (TGA/MS). Compositions containing poorly crystallized carbonate-substituted hydroxyapatite, calcium silicate hydrate and calcite as an admixture were obtained by varying concentrations of the reagents. Soaking of the composite ceramics formed from freshly precipitated synthetic solids in simulated body fluid (SBF) at 37 °C for 14 days lead to formation of the surface layer of amorphous calcium phosphate. As the calcium silicate content in the composites increases, the coating's density and thickness also increase, because silicate ions act as active sites in the process of new phase nucleation. Furthermore, prismatic calcite crystals were identified to form on the lower side of ceramics. This may be caused by an increasing of local supersaturation with respect to calcium carbonate in small-volume confinement conditions during the experiment.

Effect of reduced pH on physiology and shell integrity of juvenile Haliotis iris (pāua) from New Zealand.

The New Zealand pāua or black footed abalone, Haliotis iris, is one of many mollusc species at potential risk from ocean acidification and warming. To investigate possible impacts, juvenile pāua (~24 mm shell length) were grown for 4 months in seawater pH/pCO2 conditions projected for 2100. End of century seawater projections (pHT 7.66/pCO2 ~1,000 μatm) were contrasted with local ambient conditions (pHT 8.00/pCO2 ~400 μatm) at two typical temperatures (13 and 15 °C). We used a combination of methods (morphometric, scanning electron microscopy, X-ray diffraction) to investigate effects on juvenile survival and growth, as well as shell mineralogy and integrity. Lowered pH did not affect survival, growth rate or condition, but animals grew significantly faster at the higher temperature. Juvenile pāua were able to biomineralise their inner nacreous aragonite layer and their outer prismatic calcite layer under end-of-century pH conditions, at both temperatures, and carbonate composition was not affected. There was some thickening of the nacre layer in the newly deposited shell with reduced pH and also at the higher temperature. Most obvious was post-depositional alteration of the shell under lowered pH: the prismatic calcite layer was thinner, and there was greater etching of the external shell surface; this dissolution was greater at the higher temperature. These results demonstrate the importance of even a small (2 °C) difference in temperature on growth and shell characteristics, and on modifying the effects at lowered pH. Projected CO2-related changes may affect shell quality of this iconic New Zealand mollusc through etching (dissolution) and thinning, with potential implications for resilience to physical stresses such as predation and wave action.

Breaking the long-standing morphological paradigm: Individual prisms in the pearl oyster shell grow perpendicular to the c-axis of calcite

Cross-sections of calcitic prismatic layers in mollusk shells, cut perpendicular to growth direction, reveal well-defined polygonal shapes of individual “grains” clearly visible by light and electron microscopy. For several kinds of shells, it was shown that the average number of edges in an individual prism approaches six during the growth process. Taking into account the rhombohedral symmetry of calcite, often presented in hexagonal axes, all this led to the long-standing opinion that calcitic prisms grow along the c-axis of calcite. In this paper, using X-ray diffraction and electron backscatter diffraction (EBSD), we unambiguously show that calcitic prisms in pearl oyster Pinctada margaritifera predominantly grow perpendicular to the c-axis. The obtained results imply that the hexagon-like habitus of growing crystallites may be not necessarily connected to calcite crystallography and, therefore, other factors should be taken into consideration. We analyze this phenomenon by comparing the organic contents in Pinctada margaritifera and Pinna nobilis shells, the later revealing regular growth of calcitic prisms along the c-axis.

Compromise between mechanical and chemical protection mechanisms in the Mytilus edulis shell.

The shell of Mytilus edulis is a multilayered system for protecting this bivalve. In contrast to well-developed research on the nacre materials, the protective function of the complete M. edulis shell has not been widely studied. In particular, the question of why nacre is situated on the inner side of the shell rather than on the outer side remains unclear. Herein, the acid resistance of different shell layers was compared using etching tests and the mechanical protection performance of the shell was tested using three-point bending. Two bending loads, including static and dynamic, were applied on the shell samples from outside in (i.e. out-in bending) and from inside out (i.e. in-out bending), respectively. Our etching results show that the external prismatic calcite endows M. edulis with stronger acid resistance than if nacre was on the outside. In contrast, the static out-in and in-out bending tests reveal that a better mechanical protection of the shell against slow mechanical attacks is achieved if the nacre is on the outside. However, the shell has the same mechanical properties against dynamic mechanical attacks regardless of nacre location. Briefly, the nacre should be on the outside of the shell for better mechanical protection while the outside location of the prismatic layer offers a stronger resistance against etching. The inside natural location of nacre is a compromise between mechanical and chemical protection mechanisms against a complex survival environment. This strongly contributes to our understanding of biological design principles and further development of shell-inspired protective materials.

Comparative Study on the Sand Bioconsolidation through Calcium Carbonate Precipitation by Sporosarcina pasteurii and Bacillus subtilis

To investigate potential implications of microbial activity on sand bioconsolidation and subsurface environments, two ureolytic strains, Sporosarcina pasteurii and Bacillus subtilis were tested for the production of calcium carbonate (CaCO3). Laboratory experiments with monoculture S. pasteurii (column 1) and coculture S. pasteurii-B. subtilis (column 2) were conducted to determine urea and calcium chloride reactivity and volumetric carbonate formation. Both columns were able to consolidate sand, whereas, column 1 induced greater CaCO3 precipitation. X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed two columns with different mineralogy with calcite, and vaterite formation. Column 1 showed rhombohedral and trigonal crystals morphology, whereas column 2 developed the prismatic calcite and the spherulite vaterite crystals might be due to the differences of the micro-environment caused by the urease expression of these bacterial species. These results indicate the possibility of using those crystals to cement loose sand whereas, highlighted the importance of combining these techniques to understand the geomicrobiology found in the subsurface environments.

Physical versus Biological Control in Bivalve Calcite Prisms: Comparison of Euheterodonts and Pteriomorphs.

Multiple groups of bivalve molluscs produce calcitic shell layers, many of these broadly classified as "prismatic." Various pteriomorphian bivalves (such as oysters, pterioids, and mussels) secrete prismatic microstructures with high organic content and clear, strong biological control. However, we present the results of a detailed analysis by scanning electron microscopy (SEM), thermogravimetric analysis, and electron backscatter diffraction to characterize the calcitic prisms in two different clades within the euheterodont bivalves: the extant Chama arcana and the extinct rudists. These results show that the form of prisms constructed is both closely similar between the two taxa and significantly different from those of the pteriomorph bivalves. Most notably, C. arcana and the extinct rudists lack the clear organic outer envelopes and uniform polygonal, cross-sectional appearance. Instead, they form interdigitating crystals of very varied diameters, with some crystals encapsulating others. We advocate retaining the term "fibrillar prisms" to classify these euheterodont microstructures. These fibrillar prisms are more closely similar to abiotic speleothem deposits than to the calcitic prisms of pteriomorph bivalves. We argue that calcite prism growth in euheterodonts is dominated by abiotic constraints whereas, in pteriomorphs (such as oysters, pterioids, and mussels), it is under strong biological control.

Understanding the Precipitated Calcium Carbonate (PCC) Production Mechanism and Its Characteristics in the Liquid-Gas System Using Milk of Lime (MOL) Suspension

This study investigates the effect of operating variables and influence of milk of lime (MOL) conditions in PCC using a modified reactor. The variables includes: Ca(OH)2 feed concentration at 0.5 M–2.0 M and CO2 flow rates at 224.0 mL min–1 and 379.5mL min–1, on the particle morphology and size in the gas–liquid route precipitation. The particle morphology and texture as well as the chemical content were sufficiently authenticated using X-ray diffraction (XRD), Fourier transforminfrared spectroscopy (FTIR), scanning electron microscope (SEM) and X-ray fluorescence (XRF). Experimental data show that lower concentration (<1.0 M) favoured the formation of rhombohedra calcite crystals with the particle size below 100 nm. However, increase in concentration and gas flow rate yielded a coarser crystal particles.Two polymorphs were produced at 1M reactant, i.e. rhombohedra calcite with CO2 flow rate of 224 mL min–1 and prismatic calcite at 380 mL min–1. Molarities higher than 1 M yielded a coarser prismatic crystals, and also has a tendency to crystallize into scalenohedron species especially with higher reactant concentration.

Vertically oriented structure and its fracture behavior of the Indonesia white-pearl oyster

Structural calcites, aragonites, and the bonding organic network decide the growth, structure and mechanical properties of the mollusk bivalvia shell. Here, it was found out that the calcite prisms together with the coated organics construct another kind of ‘brick and mortar’ structure similar to the aragonite tablets. The calcite layer can be divided into three sublayers and direct evidences show that the calcite prisms are produced by two methods: nucleation and growing in the first sublayer; or fusing from the aragonites, which is quite different from some previous reports. The crystallographic orientation, micro hardness and crack propagations were tested and observed by XRD, micro harness tester, SEM and TEM. Submicron twin crystals were observed in the immature aragonite tablets. The fracture processes and the micro deformation of the aragonite tablets are detected by acoustic emission (AE) in the tensile tests, which gave the interpretation of the dynamical fracture processes: plastic deformation and fracture of the organics, and friction of the minerals at the first two stages; wear and fracture of the minerals at the third stage. Calcites and aragonites are combined and working together, like two layers of vertical ‘brick and mortar's, ensuring the stable mechanical properties of the whole shell.

Effect of electrolysis treatment on the biomineralization capacities of pearl oyster Pinctada margaritifera juveniles

The present study investigated the effect of electrolysis on the biomineralization capacities of juveniles of the mollusk Pinctada margaritifera for the first time. Size-selected individuals from two groups, “Medium” and “Large”, from a multi-parental family produced in a hatchery system were subjected to electrolysis under a low voltage current over a nine-week experimental period. The growth of the juveniles was individually monitored and assessed weekly by wet weight and shell height measurements. At the end of the experiment, mantle tissue was sampled for biomineralization-related gene expression analysis. Electrolysis significantly increased pearl oyster growth in terms of shell height and wet weight for Large juveniles from the 5th and the 2nd week, respectively, until the end of the experiment. However, differences were only significant for Medium individuals from the 7th week for shell height and from the 9th week for wet weight. Furthermore, transcriptional analysis of six known biomineralization genes coding for shell matrix proteins of calcitic prisms and/or nacreous shell structures revealed that five were significantly overexpressed in the mantle mineralizing tissue under electrolysis: three in common between the two size class groups and two that were expressed exclusively in one or the other group. Finally, we found no statistical difference of the shell thickness ratio between individuals undergoing electrolysis and control conditions. Taken together, our results indicate, for the first time in a calcifying marine organism, that electrolysis influences molecular mechanisms involved in biomineralization and may stimulate some parameters of pearl oyster growth rate.

Pinctada margaritifera responses to temperature and pH: Acclimation capabilities and physiological limits

The pearl culture is one of the most lucrative aquacultures worldwide. In many South Pacific areas, it depends on the exploitation of the pearl oyster Pinctada margaritifera and relies entirely on the environmental conditions encountered in the lagoon. In this context, assessing the impact of climatic stressors, such as global warming and ocean acidification, on the functionality of the resource in terms of renewal and exploitation is fundamental. In this study, we experimentally addressed the impact of temperature (22, 26, 30 and 34 °C) and partial pressure of carbon dioxide pCO2 (294, 763 and 2485 μatm) on the biomineralization and metabolic capabilities of pearl oysters. While the energy metabolism was strongly dependent on temperature, results showed its independence from pCO2 levels; no interaction between temperature and pCO2 was revealed. The energy metabolism, ingestion, oxygen consumption and, hence, the scope for growth (SFG) were maximised at 30 °C and dramatically fell at 34 °C. Biomineralization was examined through the expression measurement of nine mantle's genes coding for shell matrix proteins involved in the formation of calcitic prisms and/or nacreous shell structures; significant changes were recorded for four of the nine (Pmarg-Nacrein A1, Pmarg-MRNP34, Pmarg-Prismalin 14 and Pmarg-Aspein). These changes showed that the maximum and minimum expression of these genes was at 26 and 34 °C, respectively. Surprisingly, the modelled thermal optimum for biomineralization (ranging between 21.5 and 26.5 °C) and somatic growth and reproduction (28.7 °C) appeared to be significantly different. Finally, the responses to high temperatures were contextualised with the Intergovernmental Panel on Climate Change (IPCC) projections, which highlighted that pearl oyster stocks and cultures would be severely threatened in the next decade.

Heterogeneous distribution of dye-labelled biomineralizaiton proteins in calcite crystals.

Biominerals are highly ordered crystals mediated by organic matters especially proteins in organisms. However, how specific proteins are distributed inside biominerals are not well understood. In the present study, we use fluorescein isothiocyanate (FITC) to label extracted proteins from the shells of bivalve Pinctada fucata. By confocal laser scanning microscopy (CLSM), we observe a heterogeneous distribution of dye-labelled proteins inside synthetic calcite at the microscale. Proteins from the prismatic calcite layers accumulate at the edge of crystals while proteins from the nacreous aragonite layers accumulate at the center of crystals. Raman and X-ray powder diffraction show that both the proteins cannot alter the crystal phase. Scanning electron microscope demonstrates both proteins are able to affect the crystal morphology. This study may provide a direct approach for the visualization of protein distributions in crystals by small-molecule dye-labelled proteins as the additives in the crystallization process and improve our understanding of intracrystalline proteins distribution in biogenic calcites.

Controlled in Vivo Nacre Formation in Flat Pearls with Hydroxyapatite Bioceramic Nuclei

We carried out in vivo experiments of cultured flat pearl production using disc-like hydroxyapatite (HAp) bioceramics as a nucleus, with and without electric polarization treatment, and evaluated the effects of electric polarization and the quality of HAp materials on flat pearl formation. The thickness of the lamellar structures of the nacreous aragonite layers increased when polarized HAp pellets, instead of nonpolarized HAp pellets, as the nucleus, were used as the nuclei, while the thickness of the columnar structures of the prismatic calcite layers decreased. These phenomena were observed remarkably on the negative potential surface of the polarized HAp pellet. The electric polarization treatment promoted the formation rate of the nacreous lamella structure. It was speculated that electric polarization may control the physiological actions of mantle tissue and regulate the formation of the prismatic calcite and nacreous aragonite layers. The polarization treatment leads to an interference color with ...

Mineral Carbonation of Phosphogypsum Waste for Production of Useful Carbonate and Sulfate Salts

Phosphogypsum (CaSO4·2H2O) waste is produced in large amounts during phosphoric acid (H3PO4) production. Minor quantities are utilized in construction or agriculture, while most of the material is stockpiled, creating an environmental challenge to prevent pollution of natural waters. In principle, the gypsum waste could be used to capture several hundred Mt of carbon dioxide (CO2). For example, when gypsum is converted to ammonium sulfate ((NH4)2SO4) with ammonia (NH3) and CO2, also solid calcium carbonate (CaCO3) is generated. The ammonium sulfate can be utilized as a fertilizer or in other mineral carbonation processes that use magnesium silicate-based rock as feedstock, while calcium carbonate has various uses as e.g. filler material. The reaction extent of the described process was studied by thermodynamic modeling and experimentally as a function of reactant concentrations and temperature. Other essential properties such as purity and quality of the solid products are also followed. Conversion efficiencies of >95% calcium from phosphogypsum to calcium carbonate are obtained. Scalenohedral, rhombohedral and prismatic calcite particles can be produced, though the precipitates contain certain contaminants such as rare earth metals and sulfur from the gypsum. A reverse osmosis membrane cartridge is also tested as an alternative and energy-efficient method of concentrating the ammonium sulfate salt solution instead of the traditional evaporation of the process solution.

Biomineralization: Crystals competing for space.

Analysis of the growth patterns of calcitic prisms within the shell of the fan mollusc Pinna nobilis shows that growth can be predicted using grain theory and that the organic casings of the prisms set the thermodynamic boundaries.

Nanostructure of Biogenic Calcite and Its Modification under Annealing: Study by High-Resolution X-ray Diffraction and Nanoindentation

We apply advanced X-ray diffraction techniques at synchrotron microfocus beamlines in order to study the local ultrastructure of biogenic calcite with high spatial and angular resolution. Specifically, we investigate individual calcitic prisms extracted from Pinna nobilis mollusk shells with an aim to shed additional light on the structural aspects of organic/inorganic interfaces. We use annealing at elevated temperatures to destroy intracrystalline organics and measure the same prisms before and after annealing to achieve deeper understanding of the internal organization of these nanobiocomposites. Complementary nanoindentation measurements (also performed before and after annealing) allow us to elucidate the role of intracrystalline organics in increased hardness in pristine prisms and hardness reduction after annealing. We found that removal of intracrystalline organics during annealing facilitates generation of well-oriented lattice defects, which reduce the (006) diffraction intensity and are responsible for the [001]-elongated diffuse streaks nearby diffraction spots. These findings indicate the formation of internal material’s discontinuities with smooth and flat interfaces. Such nanodiscontinuities facilitate microcrack propagation under load that explains the reduced hardness of calcitic prisms after annealing.

Palaeomicrocodium: A new view on its origin

Remains of Palaeomicrocodium from the Silurian and Devonian carbonate and clay deposits from the Timan-Northern Ural region, Salair, and Western Siberia are studied using various lithological and geochemical techniques. Characters suggesting their paleoecological and geochemical specialization are discussed. It is suggested that Palaeomicrocodium structures belong to ancient lichens or actinolichens. This hypothesis is based on a number of features of Palaeomicrocodium, including the presence of typical biologically fixed microelements of soil, such as Co, Cu, Zn, Ni, and Cd, sourced from the atmosphere; presence of kerogen carbonaceous matter in prismatic calcite monocrystals of Palaeomicrocodium; identification in their structure of probable hypha-like and rhizoid-like structures; morphological similarity to extant encrusting lichens. Like lichens, Palaeomicrocodium significantly contributed to chemical weathering of rocks by excreting various organic acids, which could effectively dissolve minerals and chelate metallic cations. As a result of the weathering induced by vital function of Palaeomicrocodium, rock-forming minerals exhibit surface corrosion.

Exploring aberrant bivalve shell ultrastructure and geochemistry as proxies for past sea water acidification

AbstractThroughout much of Earth's history, marine carbonates have represented one of the most important geological archives of environmental change. Several pivotal events during the Phanerozoic, such as mass extinctions or hyperthermal events have recently been associated with ocean acidification. Nevertheless, well‐defined geological proxies for past ocean acidification events are, at best, scarce. Here, experimental work explores the response of bivalve shell ultrastructure and isotope geochemistry (δ13C, δ18O and δ26Mg) to stressful environments, in particular to sea water acidification. In this study, the common blue mussel, Mytilus edulis, was cultured (from early juvenile stages to one year of age) at four pH regimes (pHNBS 7·2 to pH 8·0). Shell growth rate and ultrastructure of mainly the calcitic portion of the shells were compared between experimental treatments. Specimens exposed to low‐pH environments show patches of disordered calcitic fibre orientation in otherwise well‐structured shells. Furthermore, the electron backscattered diffraction analyses reveal that, under acidified conditions, the c‐axis of the calcite prisms exhibits a bimodal or multi‐modal distribution pattern. Similar shell disorder patterns have been reported from mytilids kept under naturally acidified sea water conditions. In contrast, this study found no evidence that different pH regimes affect shell carbon, oxygen or magnesium isotope ratios. Based on these observations, it is proposed that: (i) stressful environments, in this case low sea water pH, predictably affect bivalve biomineralization patterns; and (ii) these findings bear potential as a novel (petrographic) proxy for ancient sea water acidification. An assessment of the applicability of these data to well‐preserved fossil shell material from selected time intervals requires additional work.

Biological control of crystallographic architecture: Hierarchy and co-alignment parameters

Mytilus edulis prismatic calcite and nacre layers exhibit a crystallographic structural hierarchy which differs substantially from the morphological hierarchy. This makes these biomaterials fundamentally different from classical crystalline materials. Morphological building units are defined by their surrounding organic matrix membranes, e.g. calcite fibers or nacre tablets. The crystallographic building units are defined by crystallographic co-orientation. Electron backscatter diffraction quantitatively shows how crystallographic co-orientation propagates across matrix membranes to form highly co-oriented low-mosaic composite-crystal grains, i.e. calcite fiber bundles with an internal mosaic spread of 0.5° full width at half maximum (FWHM) or nacre towergrains with an internal mosaic spread of 2° FWHM. These low-mosaic composite crystals form much larger composite-crystal supergrains, which exhibit a high mosaicity due to misorientations of their constituting calcite fiber bundles or nacre towergrains. For the aragonite layer these supergrains nucleate in one of three aragonite {110} twin orientations; as a consequence the nacre layer exhibits a twin-domain structure, i.e. the boundaries of adjacent supergrains exhibit a high probability for misorientations around the aragonite c-axis with an angle near 63.8°. Within the supergrains, the constituting towergrains exhibit a high probability for misorientations around the aragonite a-axis with a geometric mean misorientation angle of 10.6°. The calcite layer is composed of a single composite-crystal supergrain on at least the submillimeter length scale. Mutual misorientations of adjacent fiber bundles within the calcite supergrain are mainly around the calcite c-axis with a geometric mean misorientation angle of 9.4°. The c-axis is not parallel to the long axis of the fibers but rather to the (107) plane normal. The frequency distribution for the occurrence of misorientation angles within supergrains reflects the ability of the organism to maintain homoepitaxial crystallization over a certain length scale. This probability density is distributed log-normally which can be described by a geometric mean and a multiplicative standard deviation. Hence, those parameters are suggested to be a numerical measure for the biological control over crystallographic texture.

Brachiopod fabric, classes and biogeochemistry: Implications for the reconstruction and interpretation of seawater carbon-isotope curves and records

Shell calcite of modern and ancient brachiopods is an important proxy in reconstructing oceanographic conditions of seawater. Our investigation reveals significant magnesium and carbon isotope relationships between two classes of ancient brachiopods. Brachiopods of the extinct Class Strophomenata constructed two- or three-layer shells with a primary layer of randomized granular calcite, a secondary layer of cross-bladed laminar calcite and, at times, a tertiary layer of large prismatic calcite. Contemporaneous, but extant, Rhynchonellata also have two- or three-layer shells, but their secondary layer consists of calcite fibers instead of cross-bladed laminar calcite. Furthermore, inter-crystalline space is limited in between the fibers of the secondary layer of the Rhynchonellata but higher in the laminar secondary layer of Strophomenata. δ18O values of the two classes of brachiopods from the same stratigraphic interval of the Lopingian Nesen Formation of North Iran show a considerable overlap with no significant difference (p=0.263). In contrast, carbon isotope values are significantly different (p=0.001) between contemporaneous Strophomenata (mean: +2.18‰) and Rhynchonellata (mean: +4.13‰). An evaluation of literature data of Permian (Asselian) and Carboniferous (Visean and Serpukhovian) Strophomenata (mean: +2.32‰, N=59) and Rhynchonellata (mean: +4.94‰, N=105) confirms a similar differentiation in their carbon isotope values.Its higher magnesium contents suggest that the Strophomenata probably secreted shell calcite at a faster rate than their coeval Rhynchonellata. This process may account for the δ13C differentiation observed between specimens of these two brachiopod classes. However, the different amount and composition of the organic matter of the Strophomenata may also play a role in shaping their more negative carbon isotope signature. Thus, the class of brachiopod and their associated different fabric must be adjusted for in their δ13C results and taken into consideration during the reconstruction of Paleozoic global δ13C carbonate-based seawater curves. Invariably, in some earlier studies undetected impacts imposed by the class-fabric on δ13C may account for some of the variation or trends documented in Deep–Time seawater–13C curves reconstructed with brachiopod populations from North America, Europe and Russia.

Oriented Calcite Micropillars and Prisms Formed through Aggregation and Recrystallization of Poly(Acrylic Acid) Stabilized Nanoparticles

Though calcium carbonate crystals with various morphologies have been successfully fabricated via bioinspired methods, the mechanism underlying crystallization of one-dimensional (1D) calcite microstructures along defined crystallographic axes is poorly understood. In this paper, we first show that by combining the effects of poly(acrylic acid) (PAA) and calcite substrates we can direct the formation of calcite through an intermediate complex of PAA and Ca2+ into oriented calcite micropillars with {104} faceted coaligned platelike subunits. Moreover, in situ AFM studies under different conditions than those used in bulk experiments also lead to formation of 1D calcite microstructures. With a slight change in conditions, arrays of oriented calcite prisms with triangular cross sections are formed on calcite substrates. Though distinct in morphology, these pillars and prisms form in a similar way via anisotropic nanoparticle aggregation, growth, fusion, and reorganization. The results may provide new insights into mechanisms of biomineralization.