I found a magnetic object or rock and cannot figure out what it is..?

Question

It is smooth, and it is round on top but flat of the bottom. It has a diameter slightly larger than a quarter and is about an inch high. It's weakly magnetic, and is a dark grey color. Any ideas on what it could possibly be?

Answer 1

You have discovered an unidentified ferrous object.

Answer 2

Possibly hematite

Answer 3

Kay T is right, most probably magnetite.

The rounded shape is one of the forms of magnetite that is called "Boitriodal", I just always thought that was a fun word.

Answer 4

It may be magnetite, a type of magnetic iron ore.  There are pictures at the source site referenced.