Vaterite

Formula : CaCO3

Family: 
Carbonates
Space group: 
Hexagonal - Dihexagonal Dipyramidal HM symbol (6/m 2/m 2/m) Space Group: P 63/mmc
Dana class: 
14.1.2.1V - 14 Anhydrous Carbonates ; 14.1 Anhydrous Carbonates with Simple Formula A+ CO3 ; 14.1.2
High temperature: 
At temperatures below 15C, calcite with six-fold coordination of calcium (by oxygen atoms) was the predominant phase. Vaterite was found to have calcium coordinated to eight oxygen atoms between 25 to 60C. Thermal vibrations probably allowed for an increase in the effective radii of the calcium atoms, allowing stabilisation of the structure. Above 60C aragonite was coordinated to nine oxygen atoms, possibly accounting for its greater stability at these temperatures
Geological context: 
Vaterite is very much less common in nature than the other two forms of calcium carbonate, calcite and aragonite. It has been recorded from calcareous sediments, metamorphic rocks, and meteorites, but most known occurrences are in abnormally calcified tissues, including regenerated damaged mollusc shells, otoliths of some fishes and pathological concretions in man.

Dernière mise à jour le 25.01.2021

THERMODYNAMICS

Individual properties (298.15 K)
M
g·mol-1
 V°
cm3·mol-1
 ΔGºf
J·mol-1
 ΔHºf
J·mol-1
 Sº
J·mol-1·k-1
 CP
J·mol-1·K-1
100.087 37.630 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp. -1125799 (Ref.: Internal calculation) -1203300 (Ref.: 87gar/par) CODATA87 Garvin D., Parker V.B and White H.J., 1987. CODATA Series on Thermodynamic Properties, Hemisphere, Washington, DC. 95.120 (Ref.: 87gar/par) CODATA87 Garvin D., Parker V.B and White H.J., 1987. CODATA Series on Thermodynamic Properties, Hemisphere, Washington, DC.
CP(T) = a + b·T + ·c·T-2 (T in Kelvin)
a
J·mol-1·K-1
 b * 103
J·mol-1·K-2
 c * 10-5
J·K·mol-1
 Maier Kelley Ref.
Reaction properties

Vaterite + H+ ⇌ HCO3- + Ca+2

298.15 K, 1 bar log10K: 2.43 ΔH°r:-29630 J·mol-1 (Ref.: 87gar/par) CODATA87 Garvin D., Parker V.B and White H.J., 1987. CODATA Series on Thermodynamic Properties, Hemisphere, Washington, DC.
T(°C) 0 25 60 100 150 200 250 300
log10K 2.89 2.43 1.87 1.32 0.72 0.16 -0.44 -1.17
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-885.714427 -0.138687 49073.483172 321.459110 -2714108.349911