Constituent
Name
Magnesian Siderite
IMA name
Siderite
Class
non-silicate mineral
Compound type
carbonate
Comments
Mg-rich Siderite - previously named 'Sideroplesite' with 10-30 at% Mg, and 'Pistomesite' with 30-50 at% Mg
Chemical composition
Formula
(Fe2+,Mg,Mn2+)CO3 with Fe+Mn > Mg > 0.05
Chemical formula
(Fe2+,Mg,Mn2+)CO3
Elemental formula
(Fe2+)0.48-0.95 (Mg2+)0.05-0.5 (Mn2+)0-0.04 C O (O-)2
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
Fe2+ Iron(II) cation element 0.48 - 0.95 1.0 constituent element main
Mg2+ Magnesium(II) cation element 0.05 - 0.5 1.0 constituent element main
Mn2+ Manganese(II) cation element 0 - 0.04 1.0 constituent element main
(CO3)2- Carbonate anion chemical function 1 1.0 anionic radical main
Composition comments
with Fe+Mn > Mg and Fe+Mn between 50 and 95% - Ca < 2%, Zn < 0.2%
Chemical functions
  Function Number
(CO3)2- 1
Chemical bonds
  Bond Number
· Fe2+ · O-- 2
……C…O-2/3 3
Oxides
Formula FeO MgO MnO CO2
Mass fraction (%)

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.05

Dana

Major class
carbonates, nitrates, borates (V)
Class
anhydrous carbonates (14)
Type
with simple formula A+CO3 (14.01)
Group
Calcite group (Trigonal: R-3c) (14.01.01)
Code
14.01.01.03
Phase type
crystalline
Crystal system
trigonal
Crystal class
ditrigonal-scalenohedral
Crystal class symbol
-3m (D3d)
Crystal spacegroup
R-3c
Molar mass
100.1 - 114.3 g/mol
Density
3.96 g/cm3
Refringence type
uniaxial
Refringence sign
negative
Birefringence
0.215 - 0.242
Refraction index nα
1.785 - 1.875
Refraction index nβ
1.57 - 1.633
Color
brown, brownish yellow, greenish
Diaphaneity
translucent to subtranslucent
Luster
vitreous