https://www.theregister.co.uk/2018/07/20/gorilla_glass_6/

Four years ago at the height of smartwatch hype, it was the most desirable mineral in the world. The tech superpowers jostled to obtain supplies of the material, just as the superpowers jostled to secure their nitrate supplies* ahead of the First World War.

Sapphire would become the main ingredient in smartphone displays – as well as the smartwatches everyone would soon be wearing.** Sapphire displays were four times tougher than glass and exceptionally difficult to scratch. Panic broke out when Apple was said to have secured the world's supply of the sapphire for three years.