Granite can be slightly magnetic.
Why does a magnet stick to granite.
Long before people invented the small magnets that stick to refrigerators or the big magnets that pick up cars at the junkyard people discovered natural magnets.
Oxides of iron and titanium are responsible for this.
The most magnetic and common type is a lodestone.
This allows the minerals which form plenty of time to grow and results in a coarse textured rock in which individual mineral grains are easily visible.
Probably magnetite an fe containing mineral.
If you bring rare earth magnet towards it the magnet attracts.
Iron oxide is a fair permanent magnet ferrite magnets so if there is iron oxide in the granite it will be weakly magnetic unless the granite is laid on top of an fe containing material and your magnet is actually attracted to what is below.
We have some useless fridge magnets shaped like giant clothespegs to clip notes reminders shopping lists to useless since they get knocked off the fridge fall to the floor and the magnet pops out of the casing.
Granite is intrusive which means that the magma was trapped deep in the crust and probably took a very long time to cool down enough to crystallize into solid rock.