The gold standard of hard materials is not gold — it’s malleable and ranks at just above 2 on the Mohs scale of mineral hardness. But when it comes to the screens on smartphones, the current holy grail can be considered to be synthesized sapphire — since natural sapphire tends to be prized for different reasons. The choice material ranks in at an 8 or 9, which means that it’ll take some doing before the material exhibits scratches.
Zack Nelson, who runs the YouTube channel JerryRigEverything, decided to check out some recently launched products with some hype around sapphire screens to see if they really did live up to their essence.
The HTC U Ultra, for one, usually runs with standard glass (a 5 or 6 on the Mohs scale, good enough for your keys in the pocket). But in select markets, there’s a variation of the device where the front glass is replaced with real sapphire. How real? A scratch pick test only began to pick up results at level 8.
A Tissot watch with sapphire screen went through the same test and began scratching at the same level, but that small watchface pales in comparison to the size of the panel needed to cover the 5.7-inch display (plus the bezels!) of the U Ultra. Nelson rightly notes that the company commissioned by Apple to make sapphire displays, GT Advanced Technologies, went bankrupt in trying to get operations up to scale… for a 4.7-inch iPhone 6.
Nelson then took on Zagg’s InvisibleShield protector for the Galaxy S8, a product that has received one-star review after one-star review for its $50 price tag and its rather poor fit to the device it’s supposed to mate to. Well, we know now that you shouldn’t rely on it to be durable in spite of its “infused sapphire crystals”. The protector, mostly made of plastic with trace amounts of glass and sapphire, was damaged with a level 3 pick.
Fun fact: while the scale is strictly ordinal, not an formulaic measure, and was originally topped out with diamonds at a level 10, there are harder materials above what would be considered a 10 such as aggregate diamond products and rhenium diboride. More nuanced comparisons could be made with a ratio scale, like the one derived from the Vickers hardness test… if you can afford the time, effort and equipment to commit to it.
Then again, for our purposes, your purposes and Zack’s purposes, Mohs does just fine.