Some minerals are softer than others. How hard a mineral is can help identify it.

We measure the hardness of minerals by scratching them. In 1822, Frederick Mohs published his scale for determining a mineral’s relative hardness. On Mohs’ scale, each mineral can scratch the ones below it. Talc, for example, is softest, with a rating of 1. A diamond is hardest, with a rating of 10.

Some common objects that can be used to determine hardness include your fingernail (2.5), a penny (3), glass (5.5), and a steel file (6.5).

Cool Links:

Oxford University Natural History Museum Hardness Page - offers photos and information about each mineral in the Mohs hardness scale, including its physical characteristics and uses. Also has tips for testing hardness. Part of their Kids "Mineral Detectives" series on identification.

back to Nature Notebook