"Will it Blend?" -- harmless fun, senseless gadget murder, or... educational science experiment?
While the original iPhone 2G's shiny metallic backing was powdered by the uber-chopper, the iPhone 3G's plasticky backing, counter-intuitively, survived pretty much in one piece (one really thrashed piece, granted).
Macenstein claims their birdy pointed out "Apple never said it was plastic."
However, Steve Jobs said just that during the WWDC 2008 Keynote (at roughly the 1:26:20 mark in the podcast version): "It's got a full plastic back."
Sure, that might have been a simplification (after all, it looks like plastic), and surviving a blend and being remarkably tough and (hopefully) scratch resistant does raise some questions. So what are the the answers? Macenstein's source theorizes that:
About 2 years ago apple had a patent for an indestructible ceramic housing for handheld devices that block no wireless frequencies.” That patent is patent #20060268528, and describes a zirconia/Yttrium hybrid that may have an additional silicon coating applied “on the exterior surface to prevent cracking and protect the ceramic shell from undesirable forces as for example when the ceramic shell is dropped.”
Either way, Apple VP of Design, Jonathan Ive is known for prototyping like a madman, and really revolutionizing materials (titanium Powerbooks and dual-injected iPods anyone?), so whether its a plastic-based hybrid or not, there's probably a little magic in there somewhere.
(Just nothing fingerprint resistant... yet.)