This news is from March; I haven't seen anyone post this, and if they have, maybe some of you are unaware of this alternative.
An alternative to using pure sapphire is to laminate an ultrathin layer of sapphire with another cheaper transparent material, maintaining much of the performance advantage of sapphire at a cost comparable to that of the glass typical in mobile-phone displays.
For this purpose, GT Advanced Technologies, based in Nashua, New Hampshire, is developing a method for making sapphire sheets thinner than a human hair—much thinner than the nearly millimeter-thick glass used now on mobile phones. (The technology, originally developed for making very thin solar cells, was acquired from Twin Creeks Technologies. See “Startup Aims to Cut the Cost of Solar Cells in Half.”)