Please help ID black, glassy rock.

[raymodj]

Dug this up in our yard in Minneapolis MN. Rock Identifier says obsidian, but that seems unlikely. My first thought was a thick piece of broken glass.

So now I am just very curious.

ibb.co/6r0g4Hm
ibb.co/pdC19D5

[victor41]

The piece you have may be slag. The second picture also looks like it may show a ring like the bottom of a bottle. Is there any markings on the possible bottom?