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) | Natural | Synthetic | |
| Crystal system | Trigonal | Trigonal | Trigonal |
| Formula | NaMgFe(C2O4)3·8-9H2O | NaMgFe(C2O4)3·9H2O | NaMgFe(C2O4)3·9H2O |
| Space group | Not reported | R3c | R3c |
| a (Å) | 9.78* | 9.8367(13)* | 9.887(13)* |
| c (Å) | 36.67 | 36.902(5) | 37.03(5) |
| a/c ratio | 1:3.73–1:3.76* | 1:3.75* | 1:3.75* |
| V (Å3) | 3070 | 3092.2(7) | 3135(9) |
| Z | 6 | 6 | 6 |
| Color | Green | Greenish yellow | Green |
| Density (g cm−) | 1.69 | 1.71 (calculated) | 1.68 (calculated) |
| Zhemchuzhnikovite | |||
| Reported by Knipovich et al. (8) | Natural | Synthetic | |
| Crystal system | Trigonal | Trigonal | Trigonal |
| Formula | NaMg(Fe0.4Al0.6)(C2O4)3·8-9H2O | NaMg(Fe0.31Al0.69)(C2O4)3·9H2O | NaMg(Fe1−xAlx)(C2O4)3·9H2O† |
| Space group | Not reported | P3c1‡ | P3c1‡ |
| a (Å) | 16.67 | 16.809(7) | 16.919(2)§ |
| c (Å) | 12.51 | 12.658(6) | 12.561(2)§ |
| a/c ratio | 1:0.75–1:0.739 | 1:0.753 | 1:0.742§ |
| V (Å3) | 3001 | 3097(2) | 3113.8(9)§ |
| Z | 6 | 6 | 6 |
| Color | Green | Greenish yellow | Yellow-green |
| Density | 1.62–1.66 | 1.64 (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.