Constituent
Name
schwertmannite
IMA name
Schwertmannite
Class
non-silicate mineral
Compound type
oxide-hydroxide
Comments
formula given as $Fe^{3+}_{16}O_{16}(OH)_{12}(SO_4)_2)$ in Webmineral. Also a sulfate in Strunz classification
Constituent abundance in material
Relevance
main - major
Arrangement
single phase
Mass fraction
1.0
Chemical composition
Formula
$Fe^{3+}_{16}O_{16}(OH,SO_4)_{12-13} /bullet 10-12H_2O$
Chemical formula
Fe16O16(OH,SO4)12-13 • 10-12H2O
Elemental formula
(Fe3+)16 (O)32-36 (H)28-34 (O-)14-18 (S)3-4
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$Fe^{3+}$ Iron(III) cation element 16 constituent cation main
$O$ Oxygen element 16 constituent element main
$(OH)^-$ Hydroxide anion chemical function 8 - 10 anionic radical main
$(SO_4)^{2-}$ Sulfate anion chemical function 3 - 4 anionic radical main
$H_2O$ Water molecule 10 - 12 hydration main
Composition comments
from new formula from MinDat
Chemical functions
  Function Number Relevance
$(OH)^-$ 8-10
$(SO_4)^{2-}$ 3-4
$R-OH$ 2 main
Chemical bonds
  Bond Number Relevance
$-O-H$ 2 main
$O^--H$ 1
$\dddot - \dddot - \dddot - S \dddot - O^{-1/2}$ 4
Oxides
Formula $Fe_{2}O_{3}$ $H_{2}O$ $SO_{3}$
Mass fraction (%) 82.65 6.99 10.36
Oxides comments
determined for the old formula $Fe^{3+}_{16}O_{16}(OH)_{12}(SO_4)_2$

Strunz

Class
sulfates - chromates - molybdates - tungstates (07)
Division
sulfates (selenates, etc.) with additional anions, with H2O (07.D)
Family
with only medium-sized cations; unclassified (07.DE)
Code
07.DE.15

Dana

Major class
oxides and hydroxides (III)
Class
hydroxides and oxides containing hydroxyl (06)
Type
containing multiple cations (06.04)
Group
-Schwertmannite- group (06.04.10)
Code
06.04.10.01
Phase type
crystalline
Crystal system
tetragonal
Crystal class
dipyramidal
Crystal class symbol
4/m (C4h)
Crystal spacegroup
P4/m
Molar mass
1545.76 $g/mol$
Density
3.77 - 3.99 $g/cm^3$
Refringence type
uniaxial
Refringence sign
unknown
Birefringence
unknown
Refraction index $n_{\alpha}$
2.13 - 2.17 (calc.)
Color
browish yellow
Diaphaneity
opaque
Luster
earthy