Hardness: When you scratch one mineral against the other, the harder one will leave a mark on the weaker substance. Below is a scratched quartz crystal.
Streak: When the hardness of a mineral is tested as above, the color that is shown on the weaker mineral is the “streak.” To determine without the streak of another mineral, you can rub it against a porcelain tile. Below are two images of pyrite and cinnabar streak on a porcelain tile.
