Table 1 Crystallographic data for stepanovite and zhemchuzhnikovite.

Comparison of crystallographic and general parameters reported by Knipovich et al. (8) to the investigated natural and synthetic samples in this study.

Stepanovite
Reported by Knipovich et al. (8)NaturalSynthetic
Crystal systemTrigonalTrigonalTrigonal
FormulaNaMgFe(C2O4)3·8-9H2ONaMgFe(C2O4)3·9H2ONaMgFe(C2O4)3·9H2O
Space groupNot reportedR3cR3c
a (Å)9.78*9.8367(13)*9.887(13)*
c (Å)36.6736.902(5)37.03(5)
a/c ratio1:3.73–1:3.76*1:3.75*1:3.75*
V3)30703092.2(7)3135(9)
Z666
ColorGreenGreenish yellowGreen
Density (g cm)1.691.71 (calculated)1.68 (calculated)
Zhemchuzhnikovite
Reported by Knipovich et al. (8)NaturalSynthetic
Crystal systemTrigonalTrigonalTrigonal
FormulaNaMg(Fe0.4Al0.6)(C2O4)3·8-9H2ONaMg(Fe0.31Al0.69)(C2O4)3·9H2ONaMg(Fe1−xAlx)(C2O4)3·9H2O
Space groupNot reportedP3c1P3c1
a (Å)16.6716.809(7)16.919(2)§
c (Å)12.5112.658(6)12.561(2)§
a/c ratio1:0.75–1:0.7391:0.7531:0.742§
V3)30013097(2)3113.8(9)§
Z666
ColorGreenGreenish yellowYellow-green
Density1.62–1.661.64 (calculated)1.63 (calculated)

*The originally reported lattice parameter a for stepanovite was 9.28 Å. This is inconsistent with the a/c ratio reported in the same study, and in accepting the naming of this mineral, L. G. Berry (9) suggested it was a typographical error, with the real value being a = 9.78 Å. Herein reported a/c values for natural and synthetic stepanovite are consistent with that of Knipovich et al. (8, 9).

†For different crystals, x varied from 0.59 to 0.27.

‡Isotructural to NaMgAl(ox)3·9H2O (CCDC code YODWUK).

§Crystallographic parameters for the crystal with composition NaMg(Fe0.41Al0.59)(C2O4)3·9H2O.