The metallic component of asphalt roof shingle granules might contain copper or zinc those are not magnetic minerals.
Meteorites in gutters.
One characteristic of meteorites is that they are attracted to magnets.
If your gutters are substantially dirty or debris filled cleaning them out first and then leafing through the debris on the ground might be your best bet.
Meteors rain down on the earth every hour of every day.
Non magnetic particles washing off of roofs and into gutters onto the ground and into nearby waterways include minerals or metals used to improve the roof s resistance to algae growth and staining.
Most of these are hardly larger than a grain of rice or a pea.
Micrometeorites for your study.
If you clean your gutters all you have to do is dump the gunk into a baggie hold a strong magnet next to it and the small bit of iron common in meteorites even stony ones will cause them to be pulled over.