Apple Watch and Watch Sport — What are the differences between Sapphire and Ion-X Glass displays?

BY Kelly Hodgkins

Published 6 Mar 2015

Apple Watch

Apple advertises the Watch as having two distinct displays with the Watch Sport including an Ion-X display and the other models, the Apple Watch and Watch Edition, shipping with a sapphire glass screen. To be clear, these two materials do not comprise the entire display, but instead are the outer covers that protect the underlying flexible Retina display. Why did Apple decide to use two different display matrixes and what are the difference between the two materials? Read on to find out.

Apple chose two different display materials based on how each device is meant to be used. While the Apple Watch and Watch Edition likely will be used as timepieces first and fitness trackers second, the Watch Sport will be used first and foremost as a fitness device. As a result, Apple has designed the Watch Sport to be the lightest model in the Watch lineup and the version most able to withstand the impact of physical activities.

Ion-X Glass

The Watch Sport will ship with an aluminum casing that shaves up to 30 percent off the weight of the device and an Ion-X glass display that is lighter than sapphire and contributes less to the overall weight of the device. The Ion-X material is an aluminosilicate glass that is “fortified at the molecular level through ion exchange, with smaller ions being replaced by larger ones to create a surface layer far tougher than ordinary glass.” This process creates a material that is resistant to both scratches and impact, which is a major advantage over sapphire glass.


Sapphire is an ideal matrix for a watch and traditionally has graced the cover of luxury watches. Sapphire is very hard, second only to diamond on the hardness scale, and is extremely resistant to scratches. It also has a crystal clear transparency that makes it ideal for screens.

Sapphire’s Achilles heel is its brittleness, which makes it prone to fracturing on impact. This impact sensitivity is why Apple likely included sapphire in the Watch models that people will wear for fashion and not for fitness. This brittleness also allegedly is one of the reasons Apple last year abandoned sapphire for its iPhone models.

Gorilla Glass vs Sapphire
You can see some of the properties of sapphire in this comparison between Gorilla Glass and sapphire in this demonstration by Gorilla Glass maker Corning. In these tests, sapphire holds it own in the scratch test, but fails sooner than Gorilla Glass when placed under pressure. Apple likely has taken steps to minimize the fragility of sapphire, but this weakness should be a consideration when you are deciding which Watch model to purchase.

Which display will you buy?

The display matrix — either Sapphire or Ion-X glass– may be a consideration when you decide which Watch model to purchase. I am a sports enthusiast and will be purchasing the Sports edition so I can wear my Watch while skiing, biking and hiking without being overly concerned about cracking the screen. Which Watch model are you planning to purchase? Does the display material play a role in your decision? Let us know in the comments which model you are choosing and why.

Also check:

Apple Watch customization options — band styles, watch faces, and color choices

➤ What you need to know about Apple Watch’s hardware features

➤ Apple Watch: The hardware innovations that make the device unique