Pyrite (fools gold)
 Composition: iron and sulfur and sometimes with small amounts of cobalt, nickel, silver and gold.

Colour: yellowish gray to gray.

Streak: black with a slight green tinge.
Hardness: 6-6½

Lustre: metallic.

Cleavage: none.

Uses: sulfuric acid, Indians used to strike rocks against it making fire.

 Minerals.net