The paper reported on the research, design, and evaluation on a system to recover by sedimentation magnesium from the brine in the salt manufacture by solar evaporation in Mexico, and a system to recover by adsorbent lithium, boron, etc. from the brine of the solar pond salt field in China. In the case of Mexico, an overall recovery system was developed, but in the evaluation of economy of the system, it cannot be said that the system is feasible even if assuming that the required fresh water can be secured. It was found out that the economical efficiency largely depends upon the cost of hydrated lime and the selling price of magnesia clinker. In the case of China, a plant for production of 500 tons/year of lithium carbonate was conceptually designed to evaluate the economical efficiency. As a result, the internal profitability of the plant is not so high, approximately 6%, though continuously profitable during the operation of 15 years. It was indicated that the project was not economically very efficient. 164 figs., 44 tabs.