(Cheryl of the Clue Crew uses a magnet on a beverage can and a food can.)  In separating recyclables, a magnet is used because it will not attract aluminum, but will attract this metal, the main constituent of what we call tin cans
Ideal will be the crops that can germinate and sprout in the warm, 
moist ..... performance we have grown used to, but it will be superior to the CO/O2 
fuel system now ... abundant in the surface regolith and needs only a magnet to 
harvest.