That's a crystal wall and the spawnlocation of them got added together with the Winter Update 2018 when they added the different spawns for the Burster/Ripper/Gazer Spectres.
The different sprites:
When you push it horizontally it changes sprites depending on what sqm it is on. If you would push it vertically it wont change sprite. It seems to have 4 different sprites as shown in the image.
Spawn locations:
The locations of the following areas where you're able to get the crystal walls are part of The Dream Courts Quest.
I found my crystal walls (got some in my house) in the Haunted Tomb in Darashia where Burster Spectres are spawning. 2 of them are located here. The entrance of the Haunted Tomb is located here.
The other location where your friend (or someone else) found theirs are in the Haunted Cellar in Venore under the Outlaw Camp where Ripper Spectres and Arachnophobicas are spawning. There's 2 of them here as well, 1 at each location (see screenshot). The entrance of the Haunted Tomb is located here.
It's also possible that they may spawn in the Haunted temple in Port Hope where you find Gazer Spectres and Thanatursus. The crystal walls will get destroyed by monsters if they're pushed against a wall or another mob, so I'm not sure if they spawn in the Haunted Temple since some people were hunting there.
When you will push the crystal walls I recommend to trap the monster behind fire walls. So that they don't destroy your crystal walls. Have fun :)