When I had some quartz underground in my world, if I looked at it right, I didn't see it, instead I saw through it.

I could not recreate this, but it can possibly used for x-ray cheating on servers, and that is bad. I don't know how to recreate it, but when I put more quartz blocks in front of it, instead of stone blocks, it stopped. Please be aware of this, and if I find a way to recreate it, I will post an update. Thanks! - EDIT: This was in a single player world created inside 1.12.2