The magnesium comes out predominantly during the evapouration process as other minerals. There is a lot more sodium chloride to precipitate than magnesium thats for sure. Do some research on other evapourite producers and you will see that all the waste material builds up at the base of the large evapouration ponds or used to help build up the pond walls over time.
You seem to be a very pessimistic holder if your posting history is anything to go by. Maybe something a little more mainstream is your cup of tea?
cheers
ORE Price at posting:
21.5¢ Sentiment: LT Buy Disclosure: Held