Sapphire vs. Gorilla Glass – A Win for Precious Metals

Alongside the introduction of Apple’s new iPhone 6, the bankruptcy filing of GT Advanced Technologies made headlines last week. GTAT was Apple’s designated supplier for sapphire glass screens which analysts widely expected to make its debut on the new products. It didn’t happen, and while we can only speculate on what went on commercially, here is a technical explanation.

To begin with, what is sapphire glass? Sapphires are naturally occurring minerals reflecting light in a variety of bright colors, depending on the impurities they contain. Only very pure sapphires are completely transparent and glass-like. Various processes were developed to artificially produce pure sapphires and have been in existence for a very long time. Starting material is alumina oxide (Al2O3). Large amounts of heat and pressure are required to first turn it into a blob of sapphire called a “boule”, which is then cut into thin wafers.

The art of all of the processes used lies not only in the cutting technique but also in the way the crystals themselves are grown in the process. Crucible materials vary but there is widespread agreement that iridium crucibles, despite the process taking the metal to its physical limits, will provide for the best temperature uniformity.

Sapphire glass, which has been used in watches for a long time is already used in some other smartphones and in parts of the iPhone (the fingerprint ID buttons). It is much harder than conventional glass and more scratch resistant but not indestructible as some sources claim; depending on the type of impact it will still shatter. Alas, because of the complicated production method it is also a lot more expensive than its rival, Gorilla glass.

Gorilla glass, developed by Corning Inc specifically for the first generation iPhone, has built a reputation of strength and scratch resistivity over many years. Now available in its third generation, it is used not only by Apple but also by many other producers of smartphones, tablets and the likes.

To make Gorilla glass, Corning uses large equipment made of platinum to melt, stir and pour the glass. Other glass manufacturers around the globe do as well, making technical glass a major application for fabricated platinum. Forever increasing demands for more purity and the prevention of inclusions have pushed platinum technology forward with the products it creates.

Whichever way the market develops, platinum and iridium will play a key role in making high quality technical glass, be it sapphire or Gorilla glass. So this battle of giants already has a winner: precious metals.

By Bodo Albrecht