Calcium Isotopic Constraints on the Transition From Aragonite …

Petrographic data, including skeletal macrofossils, ooids and marine cements, suggest that the Neoproterozoic Era may have been characterized by "aragonite-dolomite seas", during which primary shallow-marine carbonates were dominated by aragonite, high-Mg calcite and dolomite (Hood & Wallace, 2012, 2018; Hood et al., …

Fibrous dolomite formation at a Miocene methane seep …

M microcrystalline dolomite matrix, B bands of stubby dolomite or Mg calcite crystals, showing dark or light contrasts, respectively, in SEM images, F fibrous dolomite crystals, E equant calcite ...

Raman spectroscopic studies of carbonates part I: High …

served in aragonite and dolomite during pressurization in contrast with the phase changes observed in calcite at 1.4 and 1.8 GPa (Fong and Nicol 1971; Gillet et al.

Contrasting intensity of aragonite dissolution and dolomite …

Dolomite formation and aragonite dissolution also show covariance on a metre-scale below 5 to 6 m, indicating that a low carbonate saturation state might enhance dolomite formation. This mechanism provides an indirect link between dolomite formation, aragonite dissolution and orbital cycles. The outcome of this study, therefore, …

(PDF) Synthesis of aragonite by carbonization …

A simple carbonization method was developed to synthesize rod-like aragonite in CaCl2-NH4Cl solution prepared from dolomite. Scanning electron microscopy and X-ray diffraction were used to...

How to Grow Calcium Carbonate Crystals …

Calcium carbonate crystals can take any of a number of forms. You can grow your own crystals that will resemble either the clear needle-like calcium carbonate prisms found naturally around hot springs …

Role of magnesium in nucleation processes of calcite, …

When seeded with aragonite, calcite is formed at a Mg/Ca molar ratio of < 1, under which condition, aragonite is converted to calcite (Bischoff & Fyfe, 1968; Bischoff, 1968 a). Above a Mg/Ca molar ...

Calcite and dolomite in intrusive carbonatites. I.

Some intrusive carbonatites exhibit poikilitic textures comprising relatively large (>0.5 mm across) oikocrysts of primary carbonate hosting numerous ovoid or lobate grains of calcite (in …

Calcite and dolomite in intrusive carbonatites. II. Trace …

The present work focuses on calcite and dolomite because these minerals account for the bulk of igneous carbonate material. Calcite is a trigonal CaCO 3 polymorph (Markgraf and Reeder 1985; Table 1) that at ambient conditions, forms only limited solid solutions with isostructural Mg, Mn and Fe 2+ carbonates, and aragonite-type …

Figure SI-1.1 Structure of (a) calcite, trigonal CaCO 3 ; (b)...

Download scientific diagram | Figure SI-1.1 Structure of (a) calcite, trigonal CaCO 3 ; (b) aragonite, orthorhombic CaCO 3 ; and (c) dolomite, trigonal (CaMg(CO 3 ) 2. The arrangement of carbonate ...

Dolomite occurrence within drift deposits, Maldives …

The percent dolomite (relative to calcite) was calculated following Goldsmith and Graf (1958). The percentage of aragonite was calculated using the method of …

Dolomites and dolomitization | SpringerLink

Furthermore, calcite and aragonite dissolve at rates many times faster than dolomite is formed, thus, the most common result of mixing zone diagenesis is rocks riddled with secondary porosity up to the dimensions of caves, with or without small amounts of dolomite (e.g., Florida, Yucatan: Back et al., 1986; confirmed by modeling: …

Saturation index (SI) for calcite, dolomite, aragonite, …

The SI values for aragonite, calcite and dolomite were >0. Thus, groundwater was oversaturated with respect to these minerals, and precipitation might occur. Given the extreme arid climate, this ...

Staining | A Color Illustrated Guide to Carbonate

Aragonite turns black whereas calcite remains colorless for some time. Mixing Feigel's Solution requires 7.1 g of MnSO 4. H 2 O; 2 to 3 g of Ag 2 SO 4; 100 cc distilled water and a 1% NaOH solution. Difficult to prepare and store. Calcite Can be distinguished from dolomite with a simple stain of Alizarin Red-S in a 0.2% HCl solution (cold ...

Calcite and Aragonite in Earth's Carbon Cycle

Aragonite and calcite have the same chemical formula, CaCO 3, but their atoms are stacked in different configurations. That is, they are polymorphs. (Another example is the of kyanite, andalusite, and sillimanite.) Aragonite has an orthorhombic structure and calcite a trigonal structure. Our gallery of carbonate minerals covers the …

Staining | A Color Illustrated Guide to Carbonate

Calcite Can be distinguished from dolomite with a simple stain of Alizarin Red-S in a 0.2% HCl solution (cold). Calcite and aragonite turn red, whereas dolomite remains colorless.

Sedimentary rock

The most widely used scheme of this type is the descriptive classification devised by the American petrologist Robert L. Folk. Sedimentary rock - Limestones, Dolomites, Calcite: Limestones and dolomites are collectively referred to as carbonates because they consist predominantly of the carbonate minerals calcite (CaCO3) and …

Precipitation of Calcite and Aragonite | Journal of the …

From pristine aragonite to blocky calcite: Exceptional preservation and diagenesis of cephalopod nacre in porous Cretaceous limestones. PLOS ONE 2018, 13 ... Fabrication of Single-Crystalline Calcite Needle-Like Particles Using the Aragonite–Calcite Phase Transition. Minerals 2017, 7 (8) ...

Dolomite and Dolomitization | SpringerLink

The crystal structure of dolomite is similar to calcite with Mg ions substituting for Ca in every other layer. To accommodate this substitution, due to differences in bond lengths between Ca–CO 3 and Mg–CO 3 (238 pm versus 208 pm, respectively), CO 3 in the Mg layer is uniformly rotated about the threefold axis relative to calcite (Reeder and …

Dolomites and dolomitization | SpringerLink

Calcite (and Aragonite) | Common Minerals

In the Upper Midwest region, calcite and dolomite are the most important minerals that comprise the carbonate rock layers that cover the region's southeastern extent. These …

The genesis of calcite and dolomite carbonatite

We address the contention that calcite cannot crystallize from a dolomitic liquid formed by direct mantle melting, and must therefore have crystallized from a …

Aragonite, breunnerite, calcite and dolomite in the CM …

Grains of aragonite, breunnerite, dolomite and type 1a calcite, and a proportion of the type 1b calcite grains, were formed early by cementation of pores …

Upper Ediacaran fibrous dolomite versus Ordovician fibrous …

Without the characteristic botryoidal fabric (Fig. 4 D and F), aragonite-to-dolomite neomorphism seems unlikely (Hu et al., 2020a). In addition, optically syntaxial replacement of fibrous aragonite by dolomite is unlikely due to the different crystal systems of the two minerals (Shuster et al., 2018). Currently, the most likely option is …

Mineral

Dolomite [CaMg (CO 3) 2 ], kutnohorite [CaMn (CO 3) 2 ], and ankerite [CaFe (CO 3) 2] are three isostructural members of the dolomite group. The dolomite structure can be considered as a calcite-type structure in which magnesium and calcium cations occupy the metal sites in alternate layers. The calcium (Ca 2+) and magnesium …

Experimental study of the aragonite to calcite transition …

1. Introduction. The relative stability fields in P, T space of the two most common polymorphs of CaCO 3, calcite and aragonite, are well known (Carlson, 1983, Tucker and Wright, 1990).Aragonite is the high pressure phase and forms stably in metamorphic rocks. Nevertheless, during exhumation it is only rarely preserved and …

(PDF) Aragonite, breunnerite, calcite and dolomite in the …

The pore spaces that remained after precipitation of aragonite, dolomite and breunnerite cements were occluded by calcite. Following completion of cementation, the carbonates were partially ...

Production and characterization of synthetic aragonite prepared …

We successfully synthesized pure aragonite crystals in the reaction temperature range of 40–70 °C at a fixed CO 2 flow rate of 3.00 l/min, and at a stirring speed of 750 rpm. The d 90 values of the aragonite crystals at various temperatures ranged from 18.47 to 25.99 μm. We fit the experimental results by a single-term …

Limestone vs Dolomite: What Are They, And What's The …

Limestone is an occurring type of sedimentary carbonate rock found on Earth's surface. It is formed when crystals of calcium carbonate precipitate out of water containing dissolved calcium. Limestone is composed of minerals such as calcite and aragonite. Limestone consists of 80 percent calcite and Dolomite with more than 50% calcium carbonate.

Calcite and Aragonite Precipitation Under Controlled …

The predominance of aragonite at high solution Mg/Ca and low supersaturations is attributed to a relative decrease in calcite growth rates as a result of increasing incorporation of Mg 2+ in the calcite lattice at higher solution Mg/Ca ratios. As suggested by abundant experimental work, increasing solution Mg/Ca decreases the …

Polycrystalline calcite to aragonite transformation kinetics

The kinetics of the calcite to aragonite transformation have been investigated using synthetic polycrystalline calcite aggregates, with and without additional minerals present. The reaction progresses as a function of time were measured at four temperature/pressure conditions: (1) 550 °C/1.86 GPa; (2) 600 °C/2.11 GPa; (3) 650 …