https://www.chemicalonline.com/doc/dow-to-exit-magnesium-business-0001
As I thought. Gone, and good riddance
About 1979, Dow built a semi-plant mag purification plant as the final step before going to full size commercial. The responsible big dog manager decided a pilot plant wasn't needed for whatever reason. So…. It was $10MM capital down the tubes when the process didn't pan out as projected.
I was doing some work adjacent to the huge clarifiers in Plant B that (about 500ft diameter IIRC) used to remove precipitated contaminant inorganics from the seawater. One of the clarifiers had sheared a pin from torque overload on the plow arms and the clarifier was drained to remove packed in solids. They dropped a small bulldozer in the clarifier to push solids to the sidewall and a scoop would reach down to grab a bucket full for loading into dump trucks. IIRC correctly, the raw seawater intake for Plant A and Plant B mag production was something like 200-250K gpm. Lotta water….