Mineral phase
IMA name
Huntite
Secondary names
Magnesium calcium carbonate; Mg-Ca carbonate
IMA Code
Hun
Type
Class
non-silicate mineral
Compound type
carbonate
Chemical composition
Formula
$CaMg_3(CO_3)_4$
Chemical formula
CaMg3(CO3)4
Elemental formula
(Ca2+) (Mg2+)3 C4 O4 (O-)8
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$Ca^{2+}$ Calcium cation element 1 constituent cation main
$Mg^{2+}$ Magnesium(II) cation element 3 constituent cation main
$(CO_3)^{2-}$ Carbonate anion chemical function 4 anionic radical main
Chemical functions
  Function Number
$(CO_3)^{2-}$ 4
Chemical bonds
  Bond Number
$\cdot Ca^{2+} \cdot O^{-}-$ 2
$\cdot Mg^{2+} \cdot O^{-}-$ 6
$\dddot - \dddot - C \dddot - O^{-2/3}$ 3
Oxides
Formula $CaO$ $MgO$ $CO_{2}$
Mass fraction (%) 15.88 34.25 49.87

Strunz

Class
carbonates - nitrates (05)
Division
carbonates without additional anions, without H2O (05.A)
Family
Alkali-earth (and other M2+) carbonates (05.AB)
Code
05.AB.25

Dana

Major class
carbonates, nitrates, borates (V)
Class
anhydrous carbonates (14)
Type
with Compound Formula A+2B++2(CO3)4 (14.04)
Group
-Huntite- group (14.04.03)
Code
14.04.03.01
Phase type
crystalline
Crystal system
trigonal
Crystal class
trapezohedral
Crystal class symbol
32 (D3)
Crystal spacegroup
R32
Molar mass
353.03 $g/mol$
Density
2.696 $g/cm^3$
State NTP
solid
Refringence type
uniaxial
Refringence sign
negative
Refraction index $n_o$ (w)
1.622
Refraction index $n_e$ (e)
1.615
Pure color
colorless
Color
white, lemon white
Luster
earthy
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