Before you read on, take a quick look at this Quora post, answering the question What will the iPhone 8 be made of?
That post sells the idea that the iPhone 8 will be made primarily from ZrO2 – Zirconian Ceramics, made famous by the Space Shuttle as a thermal barrier and an option on the newest Apple Watch.
The linked post, from Atomic Delights, is a strong rebuttal to that Quora post and a bit of a love letter to aluminum.
Beautifully written, a terrific read.