This entire website and company reads like a penny pink sheets stock scam. "Magrathea sells metal using multi-year supply agreements in countries with enforceable contract law. Supply agreements allow our partners to build in magnesium with confidence. We prevent price instability from Chinese trade manipulation so the innovative products of our partners can succeed in the market." There's absolutely no information o…
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.