Metal from Slag

[ScegfOd]

[Engineer]
Slag is what is left over after all the metal you can squeeze out with your current furnace technology has already been squeezed out.
It is a mixture of various goodies that make your iron brittle and shitty; and you just got rid of that shit, so go dump it in a hole somewhere

HOWEVER, slag being shitty and brittle crap isn't all bad. It's pretty similar to stone and I've heard of some people using slag to make housing insulation so certain kinds of slag cant be too different from stone (dolomite, a kind of stone, is what it would be replacing/mixed in with).
Being able to get some usable stone or brick out of slag wouldn't be entirely unrealistic.
[/Engineer]

of course, it's up to our generous Devs whether or not it makes sense from a gameplay standpoint.

[ZantetsukenX]

The possibility of making a curio that uses slag as an ingredient is always possible.

[Zampfeo]

Slag glass

[pinzig]

slag as paving perhaps paving with slag creates mountain/cave floor looking spaces.

[ScegfOd]

slag as paving perhaps paving with slag creates mountain/cave floor looking spaces.

this
though maybe the graphic could be it's own slag pavement that is unique

[DatOneGuy]

People have suggested uses for slag for quite some time now.
From windows to tempered glass to paving, all of it.