How tough is the Apple Watch? People have been putting the new device through the wringer to see if it's as durable as some want it to be or if it's just a fragile fashion accessory. An integral part of this testing is checking the screen's durability. The Apple Watch uses a sapphire glass screen, just like the iPhone 6.

The sapphire glass wasn't well prepared for the iPhone 6's release, which was partly due to Apple's sapphire glass supplier having financial difficulties, according to the International Business Times. Apple claims it has improved the material, but is it as good as Apple and sapphire glass makers say? That's what YouTuber "Unbox Therapy" recently tested. In the video, the host tests the Apple Watch with a basic diamond tester, which can determine whether a diamond is real or fake. The YouTube host also attempts the same thing with the Apple Watch Sport, LG G Watch R, iPhone 6 and a Tissot watch that the makers say has a sapphire crystal display.

"The results of the test confirm that the Apple Watch does have a sapphire crystal display as advertised, with the diamond tester recognizing the thermal conductivity of the scratch-resistant material. The verified Tissot watch also displays a reading on the meter, while the Apple Watch Sport, LG G Watch R and iPhone 6 do not yield any results because all three devices have traditional or ion-strengthened glass displays" reports MacRumors.

Sapphire glass is typically more scratch-resistant than normal glass. The process for making sapphire glass involves cutting it with a diamond-encrusted wire and polishing it with diamond pellets.

Earlier this week, CNET washed, submerged, boiled, grated, spilled on, dropped and finally smashed the Apple Watch to see how well it would hold up. Tech YouTuber FoneFox took it to the next level by wearing the device underwater for an extended period.