Saw this person log on whilst I was in-game last night, would have posted this sooner but lb wasn't working. When he logged on I decided to tp to him vanished, there name sounded suspicious to me, and saw them in a mine with no torches. They then dug straight towards gold, not orderly strip mining, just a random digging towards it. After them warping to their house and quite a few shops, they then warped back to their home and did a bit of farming. A few minutes later they walked to the side of there house and dug straight down, and reached iron then digging a bit further down and slightly off a bit to the left found another patch of iron.
After seeing this I decided to look around the house and found yet another shaft straight down to iron then to bedrock and more iron/redstone that had been mined by them.
I came to the conclusion they were either using a X-ray texturepack allowing them to see straight down, or the X-ray mod.
Here are some screenshots, sorry some are a bit dark and gloomy, he doesn't use torches, another sign of a x-rayer and I added the ones you can see: http://imgur.com/a/9AJtD#CFuDxgH
After seeing this I decided to look around the house and found yet another shaft straight down to iron then to bedrock and more iron/redstone that had been mined by them.
I came to the conclusion they were either using a X-ray texturepack allowing them to see straight down, or the X-ray mod.
Here are some screenshots, sorry some are a bit dark and gloomy, he doesn't use torches, another sign of a x-rayer and I added the ones you can see: http://imgur.com/a/9AJtD#CFuDxgH