A follow up to http://d-infinity.net/blog/derek-holland/mutant-minerals-and-plants
Even though the wonders of Gamma World and Mutant Future that most think of are biology, culture and technology, that excludes the abiotic part of the setting. A geologist or chemist should be as mind blown as a zoologist or mycologist while exploring the wastes. Here are some materials and processes that, for the most part, are the result of the war (rather than what happened after):
Breccia (conglomerate) of plastic and concrete should be fairly common as the mineral component protects the adhesive from some weathering. The breccia is the result of buildings being melted by atomic and other heat producing weapons. It will break apart, though that could take centuries. Or until a plastic eating organism chows down.
Impact gems are glass formed by kinetic weapons (solid objects dropped from orbit). They have different appearances and physical traits that depends on the impurities at the site of formation. Most are like obsidian, which is a natural glass, but others can be very strange in look and behavior (see below).
Some concrete formed when dust from pulverized building mixed with water. This can have two effects- making exploring ruins more difficult as it is hard to tunnel through and protecting artifacts and other loot from decay due to exposure. Just don't use explosives to get them out.
Sand, silt and ash that is toxic and/or radioactive. The ash survives because people collected it and made reliquaries (i.e. they are though to hold remains of Ancients). Hopefully the containers, usually bottles, have leaded surfaces and the sealed well as a release could very well be lethal.
Weird stuff like what I posted before, magnetic (which may attract non-metals) and EMP emitting substances. All of these are the result of alien or superscience weapons. Some impact glass should have some of these traits.
Semi-permanent fog banks that are the result of materials that sublimate. They will eventually fade, but that could take decades or centuries. They can also appear in the material was buried and recently dug up or otherwise exposed to air.
Hot springs, fumeroles and geyers are the result of energy sources that still burn hot while buried (like busted atomic cells). Most are water, including fossil water, but some can be of other liquids. Like fog banks, they can appear suddenly if the power source starts to heat up or a source of liquid reaches one that was previous dry . The PCs may create these by accident if they break some artifacts.
Even the occasional use of such materials and processes can go a long way into making the setting more wondrous and exploring more interesting. In MF settings that I design, there is few reasons not to dig into walls and floors looking for spare parts and lost loot.
