The hardness of a mineral is often defined by using Moh's Scale of Relative Hardness. This scale was developed in 1822 by Friedrich Moh to measure the hardness of minerals. The idea behind Moh's Scale was that minerals or substances with a lower hardness could not scratch minerals or substances with a greater hardness.

1. Talc
This is the softest of the minerals and can easily be scratched with a fingernail. It is used in paint, paper,and talcum powder. Soapstone consists mainly of talc.

2. Gypsum
This mineral can barely be scratched with a fingernail. It is used for plaster of paris, wallboard, and interior plaster. Alabaster is a fine-grained variety of gypsum.

3. Calcite

You can barely scratch calcite with a copper penny. Limestone and marble are varieties of calcite.

4. Fluorspar
This mineral can easily be scratched with a knife blade. It is a beautiful mineral occurring in many different colors and is mainly used for making steel.

5. Apatite
Can barely be scratched with a knife blade. Its greatest use is as a source of phosphorus for common fertilizers.

6. Feldspar
This mineral cannot be scratched by a knife blade but it can easily be scratched with window glass. It is found in most igneous rocks, and is an essential component of crystalline rocks such as granite, gabbro, and basalt.

7. Quartz
This is the most common mineral and often the most beautiful. It will easily mark steel and hard glass. Quartz makes up the sand on our seashores and is found in sandstone and quartzite. Some varieties of quartz are used as gemstones. These include amethyst, bloodstone, crystal, flint, and onyx.

8. Topaz
It is harder than other common materials and also highly prized as a gem.

9. Corundum

This mineral will scratch Topaz. Clear blue varieties make the sapphire, and clear red varieties make the ruby. Corundum is often used as an abrasive.

10. Diamond
This is considered the hardest mineral and will scratch corundum as well as all minerals on this scale. The hardness of the diamond is greater than any other known substance natural or artificial. Diamond is pure carbon and highly prized as a gemstone.