[marcosdumay]

Somehow we should expect them to be able to purify magnesium from brine, and yet not be on the market selling lithium. That's extremely odd.

Edit: Turns out that no, it's simpler to separate magnesium and calcium than lithium, even those existing in much smaller amounts. Those metals form many solid ionic compounds, with anions that would keep sodium and lithium soluble.

[runnerup]

The majority of the magnesium used for WW2 explosives was produced from brine near Freeport, TX. (I think? need to double-check this)

Edit: During WW2 additional production facilities around the USA were brought online. Before and after WW2, except for a moment during the Korean War, Dow's facility in Freeport, TX was the only producer of magnesium in the USA. It peaked in capacity in the 1970's. There were several other endeavors by other companies to produce magnesium over time with different technologies. Most magnesium production in the USA has been eliminated for economic reasons.