It has been suggested in another threat , and I know there is no point in suggesting now as we are changing the engine or whatever.
But i would love to see this element in the future. Brick [BRIK]
This would be a Solid for building sims , like the citys . The Brick would be immune to fire but at Very High temps ( 3000C ) would start to melt into lava. It would be pressure sensitive , but not as BMTL or GLASS. A tad bit more resistant at about pressure. It should crack into STNE , CNCT or DUST. It would help a lot in creating buildings as BMTL is too sensitive , and a house made of metal , meh...
Well. What about rust? (sorry if already suggested, i don't remember). When water touches metal/breakable-/broken metal water eats it (like acid, but slowly) and creates rust.