I swear I remember reading that (at least, adult) Aliens are silicon based, but I can't remember where. Can someone help me out? Is it from the expanded universe?
'Alien' has Ash talking about the facehugger shedding its cells and replacing them with polarized silicon, but that doesn't necessarily mean a whole lot. He also says it has an outer layer of protein polysaccharides, which are carbohydrates (carbon based).
I might check the Weyland-Yutani Report later because I have a hunch that might say something, but I swear that Aliens being silicon based is a long-standing thing from the EU for some reason.