Iron filings

[1] As the name suggests, iron filings can be obtained from metal working operations as the scrap material filed off larger iron and steel parts.

[2] They are very often used in science demonstrations to show the direction of a magnetic field.

Since iron is a ferromagnetic material, a magnetic field induces each particle to become a tiny bar magnet.

The south pole of each particle then attracts the north poles of its neighbors, and this process is repeated over a wide area creates chains of filings parallel to the direction of the magnetic field.

They are also used in some toys, most famously Wooly Willy, where they serve to mimic hair on a cartoon face.