# A Review of Evaporite Beds Potential for Storage Caverns: Uncovering New Opportunities
## 2 Evaporites and Bedded Evaporite Deposits
### Evaporite Minerals  
In the previous section, the marine and non-marine sources of brine and depositional environments of evaporites were explained. The types of evaporite minerals that form depend on the brine chemistry in these environments. For marine evaporites, the primary minerals are halite and/or anhydrite, though other minerals like evaporitic carbonates and potash salts are also present. Non-marine brines, on the other hand, produce three main types of evaporites: soda ash, salt-cake, and borate deposits [60]. According to [92], non-marine evaporite basins contain five major water types from which various saline minerals are produced: (1) Ca-Mg-Na-(K)-Cl, (2) Na-(Ca)-SO\({}_{4}\)-Cl, (3) Mg-Na-(Ca)-SO\({}_{4}\)-Cl, (4) Na-CO\({}_{3}\)-Cl, and (5) Na-CO\({}_{3}\)-SO\({}_{4}\)-Cl waters. Some minerals, such as halite and gypsum, are found in both marine and non-marine environments [62; 93], as shown in Table 2, which lists major saline minerals and their occurrence in different settings [94]. Regardless of their marine or non-marine origin, evaporite minerals can be categorized into three main groups, as identified in [48]: carbonate minerals (e.g., calcite and dolomite), sulfate minerals (e.g., anhydrite and gypsum), and chloride minerals (e.g., halite and sylvite). A list of the most common evaporite minerals can be found in [95]. \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Mineral** & **Composition** & **Marine** & **Non-Marine** \\ \hline Anhydrite & CaSO\({}_{4}\) & X & X \\ Aphthitalite (glaserite) & K\({}_{2}\)SO\({}_{4}\)-(Na, K)SO\({}_{4}\) & & X \\ Antarcticite & CaCl\({}_{2}\)-6H\({}_{2}\)O & & X \\ Aragonite & CaCO\({}_{3}\) & X & X \\ Bischofite & MgCl\({}_{2}\)-6H\({}_{2}\)O & X & X \\ Bloodite (astrakanite) & Na\({}_{2}\)SO\({}_{4}\)-Mg SO\({}_{4}\) 4H\({}_{2}\)O & X & X \\ Burkeite & Na\({}_{2}\)CO\({}_{3}\):2 Na\({}_{2}\)SO\({}_{4}\) & & X \\ Calcite & CaCO\({}_{3}\) & & X \\ Carnallite & MgCl\({}_{2}\):KCl\(\cdot\)6H\({}_{2}\)O & X & X \\ Dolomite & CaCO\({}_{3}\)-MgCO\({}_{3}\) & X & X \\ Epsomite & MgSO\({}_{4}\)\(\cdot\)7H\({}_{2}\)O & X & X \\ Gaylussite & CaCO\({}_{3}\)-Na\({}_{2}\)CO\({}_{3}\) 5H\({}_{2}\)O & X & X \\ Glauberite & CaSO\({}_{4}\)-Na\({}_{2}\)SO\({}_{4}\) & X & X \\ Gypsum & CaSO\({}_{4}\)\(\cdot\)2H\({}_{2}\)O & X & X \\ Halite & NaCl & X & X \\ Hanksite & 9 Na\({}_{2}\)SO\({}_{4}\) 2 Na\({}_{2}\)CO\({}_{3}\)-KCl & & X \\ Hexahydrite & MgSO\({}_{4}\)\(\cdot\)6H\({}_{2}\)O & X & X \\ Kainite & MgSO\({}_{4}\)-KCl\(\cdot\)11/4H\({}_{2}\)O & X & X \\ Kieserite & MgSO\({}_{4}\)\(\cdot\)H\({}_{2}\)O & X & X \\ Leonhardtite & MgSO\({}_{4}\)\(\cdot\)4H\({}_{2}\)O & X & \\ Leonite & MgSO\({}_{4}\)\(\cdot\)K\({}_{2}\)SO\({}_{4}\)-4H\({}_{2}\)O & X & X \\ Mirabilite & Na\({}_{2}\)SO\({}_{4}\)\(\cdot\)10H\({}_{2}\)O & X & X \\ Nahcolite & NaHCO\({}_{3}\) & & X \\ Natron & Na\({}_{2}\)CO\({}_{3}\)\(\cdot\)10H\({}_{2}\)O & & X \\ Pentahydrite & MgSO\({}_{4}\)\(\cdot\)5H\({}_{2}\)O & X & \\ Pirssonite & CaCO\({}_{3}\)-Na\({}_{2}\)CO\({}_{3}\)\(\cdot\)2H\({}_{2}\)O & & X \\ Polyhalite & 2 CaSO\({}_{4}\)\(\cdot\)MgSO\({}_{4}\)\(\cdot\)K\({}_{2}\)SO\({}_{4}\)\(\cdot\)2H\({}_{2}\)O & X & X \\ Shortite & 2 CaCO\({}_{3}\)-Na\({}_{2}\)CO\({}_{3}\) & &? \\ Sylvite & KCl & X & X \\ Tachyhydrite & CaCl\({}_{2}\)-2 MgCl\({}_{2}\)-12H\({}_{2}\)O & & X \\ Thenardite & Na\({}_{2}\)SO\({}_{4}\) & & X \\ Thermonatrite & Na\({}_{2}\)CO\({}_{3}\)\(\cdot\)H\({}_{2}\)O & & X \\ Trona & NaHCO\({}_{3}\)\(\cdot\)Na\({}_{2}\)CO\({}_{3}\)\(\cdot\)2H\({}_{2}\)O & & X \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Major saline minerals (marine, non-marine, or both settings) [94]. Research has also indicated that evaporite minerals precipitate in a specific sequence [94; 96; 97]. Carbonates are the first to precipitate when brine reaches twice the concentration of seawater, at a density of approximately 1.10 g/cm\({}^{3}\). As brine concentration increases to five times that of seawater, with a density of around 1.13 g/cm\({}^{3}\), gypsum begins to precipitate.