I've done a few more tests on the object:

- The object is magnetic (but not very strong)

-> magnet and object attract each other
-> object and other metal do not attract

Funny this is my minelab and my Garret detector at the
Object make no sound.

What is magnetic (metallic) but not indicated by a metal detector?

I pulled the object over a fine whetstone.
- There was an abrasion which one recognizes on the object
- But no colored abrasion on the grindstone
- The object also remained black in the place