Now consider pyrite, a brassy yellow mineral that looks like gold.

Pyrite. It is brassy yellow and shiny like metal.

Hadley rubs the pyrite across a white tile, and it leaves a greenish black mark.

Hadley rubs the pyrite across the white tile.

The mark pyrite leaves on the white tile.

The color of the mark a mineral leaves on a white tile is called its streak.

Hadley rubs the quartz and the calcite on the tile too.

Both leave a white mark, so streak does not tell those two apart.

Gold leaves a yellow streak, so the greenish black streak shows this is pyrite, not gold.

The finished table for quartz, calcite and pyrite.