Morgoth vs Fingolfin 3 image - The Fellowship

The Following excerpt is from the Quenta Silmarillion, Chapter XVIII: Of the Ruin of Beleriand and the Fall of Fingolfin. "Then Morgoth hurled aloft Grond, the Hammer of the Underworld, and swung it down like a bolt of thunder." So, yes, you're correct, but since Tolkien never described Grond, I guess it's up to the artist to use their own imagination as to what it looked like. If you ask me, this makes the most sense, (as opposed to a big hammer) because it looks like the mace used by Sauron in the Fellowship of the Ring, and since Sauron pretty much fashioned his armor as a copy of Morgoth's armor, it makes sense that he would do the same with his weapon.