I think it would make more sense that alien craft would either be made of composite materials[nano-tubes and etc] or biological[dna structures(Sciam wrote an article about their use in the release of dyes at the presence of explosive chemicals) and etc] in nature. Which, really makes it a non-sequitor to say any raw material means it's from outerspace. When a big semitruck[or plus] sized craft smacks down in downtown whatever, then that'll be proof of space truckin' non-humans.

-- Bridget

__________________
"Contrary to the ecologists, nature does not stand still and does not maintain the kind of "equilibrium" that guarantees the survival of any particular species - least of all the survival of her greatest and most fragile product: man." -- Ayn Rand