Table 2. Stability of rhomboclase.
Resulting mineralogy after a 1-month suspension of rhomboclase (rbc) in varying concentrations of sulfuric acid. Acid concentration calculation takes into account H2O released from mineral transformation. Rhomboclase is stable up to concentrations of 74.2 wt % and transforms into acid ferric sulfate (AFS) within hours to days in higher concentrations (Fig. 1). It is observed that copiapite transforms into rhomboclase within 9 days in 51.3 wt % sulfuric acid (fig. S6) and follows the same rhomboclase to AFS transformation in higher concentrations.
| T = 298.15, P = 1 bar | ||||
|---|---|---|---|---|
| Ex.No | H2SO4 wt % | Solution (g) | Solid (g) | Resulting mineralogy (XRD and Raman) |
| rbc-1 | 51.3 | 5.9916 | 0.5453 | rbc |
| rbc-2 | 74.2 | 6.7096 | 0.4445 | rbc |
| rbc-3 | 79.1 | 6.8232 | 0.3000 | AFS |
| rbc-4 | 83.5 | 6.9012 | 0.2792 | AFS |
| rbc-5 | 90.1 | 6.5734 | 0.0611 | AFS |
| rbc-6 | 97.4 | 7.2205 | 0.2735 | AFS |