Gold and sapphire. No, we're not talking about Rolex wristwatches but the iPhone 5S. All rumors of course.
The reason? Sapphire prevents the button from being scratched and a slightly convex shape creates room for the fingerprint sensor, according to the analyst.
Note that there has also been speculation that the 5S' touch display would handle fingerprint sensing chores.
A fingerprint reader could pave the way for more secure mobile payments or be used as a more secure way to access a user's Apple account.
The KGI analyst also mentioned the new iPhone 5S will keep the 8-megapixel sensor but make other camera improvements.
Another notable iPhone 5S rumor has it sporting a new Apple A7 processor.
Apple may introduce new iPhones on September 10.