If you had to create a modern 5 category exhaustive folksonomy of ALL materials, like the earth-fire-water-wind-ether of the alchemists, what would your 5 base classes be? Should cover all familiar modern materials.
Well, I was starting off with solid, liquid, gas ... plasma(?), empty space(??). OK, I can't get to 5 and keep it folks(onom)y, but the first three seem like pretty commonsense categories even though also science-y.
Unlike the alchemists by 'materials' do you assume solid?