Existing Apple suppliers say GT Advanced promised too much, didn't diversify enough

Existing Apple suppliers say GT Advanced promised too much, didn't diversify enough: For starters, GT Advanced told Apple it would be able to build extraordinarily large sapphire boules sized at 578 pounds — double the size of competing products. But GT Advanced struggled to manufacture boules of sapphire at that size, experiencing poor yield rates and producing tons of material that was unusable.