Mineral phase
IMA name
Fairchildite
Secondary names
Potassium calcium carbonate; K-Ca carbonate
IMA Code
Fch
Type
Class
non-silicate mineral
Compound type
carbonate
Chemical composition
Formula
$K_2Ca(CO_3)_2$
Chemical formula
K2Ca(CO3)2
Elemental formula
(K+)2 (Ca2+) C2 O2 (O-)4
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$K^+$ Potassium(1+) cation element 2 constituent cation main
$Ca^{2+}$ Calcium cation element 1 constituent cation main
$(CO_3)^{2-}$ Carbonate anion chemical function 2 anionic radical main
Chemical functions
  Function Number
$(CO_3)^{2-}$ 2
Chemical bonds
  Bond Number
$K^+ \cdot O^{-}-$ 2
$\cdot Ca^{2+} \cdot O^{-}-$ 2
$\dddot - \dddot - C \dddot - O^{-2/3}$ 3
Oxides
Formula $K_{2}O$ $CaO$ $CO_{2}$
Mass fraction (%) 39.53 23.53 36.94

Strunz

Class
carbonates - nitrates (05)
Division
carbonates without additional anions, without H2O (05.A)
Family
Alkali and alkali-earth carbonates (05.AC)
Code
05.AC.20

Dana

Major class
carbonates, nitrates, borates (V)
Class
anhydrous carbonates (14)
Type
with Compound Formula A+2B++(CO3)2 (14.03)
Group
Fairchildite series (14.03.03)
Code
14.03.03.01
Polymorphs
Phase type
crystalline
Crystal system
hexagonal
Crystal class
dihexagonal-dipyramidal
Crystal class symbol
6/mmm (D6h)
Crystal spacegroup
P6(3)/mmc
Molar mass
238.29 $g/mol$
Density
2.446 $g/cm^3$
State NTP
solid
Refringence type
uniaxial
Refringence sign
negative
Birefringence
0.0540
Refraction index $n_o$ (w)
1.532
Refraction index $n_e$ (e)
1.478
Pure color
colorless
Color
colorless
Diaphaneity
transparent
Luster
vitreous
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