The LG G6 stood in all the the MIL-STD-810G military standard test from what I've read on several website, although for some reason LG it didn't get the stamp of approval and wasn't mentioned anywhere in the press release or the announcement event. Anyways, this was mentioned one many websites that wrote about the LG G6 like thenextweb.com. This means that the LG G6 is highly resilient to drops and scratches.
There is some confusion about which type of Gorilla Glass is used for the LG G6. According to techradar.com, the phone use two different glasses for the rear and front. The rear one uses Gorilla Glass 5 and the front glass is Gorilla Glass 3. This probably explains its excellent effectiveness against scratches. In fact, there are already videos on YouTube of people who ran a scratch test using a knife and keys on the back of the LG G6 to see if it can be easily scratched.
Here is the first video that was also posted on phonearena.com.
You can see that these guys took a sharp knife and tried to scratched the back of the LG G6 phone from various angles. After a few seconds they clean the back with a napkin and at least for my surprise, there were no scratches. It's very easy to notice scratches on a reflective surface. I think that this is the reason why LG opted for Corning GG5 for the back. Gorilla Glass 5 has a high degree of protection against drops compared to previous versions.
Overall, it's nice to see that the phone use Gorilla Glass for both the front and the back, which provides the LG G6 with very good protection from drops and scratches.