MohsSkala

The Mohs scale of mineral hardness, commonly known as the Mohs scale, is a qualitative scale that characterizes the scratch resistance of minerals. It was devised by German mineralogist Friedrich Mohs in 1812 and remains in use today as a simple reference in geology and mineralogy. The scale assigns integers from 1 to 10, with higher numbers indicating greater hardness.

The standard reference minerals are talc (1), gypsum (2), calcite (3), fluorite (4), apatite (5), orthoclase feldspar (6), quartz (7), topaz (8), corundum (9), and diamond (10). In practice, to test hardness you try to scratch a specimen with the reference minerals, or you check whether the specimen can scratch a reference mineral. If a mineral A can scratch mineral B, A is harder than B.

The Mohs scale is relative and non-linear; it provides a quick, ordinal ranking rather than precise measurements of hardness. Factors such as crystal orientation, grain size, surface finish, and moisture can influence scratch results. The scale is widely used for field identification, rough sorting of rocks and minerals, and selecting abrasives, but modern hardness testing for engineering purposes often uses quantitative methods such as Vickers or Rockwell tests.

In education and outreach, the Mohs scale serves as a straightforward teaching tool for illustrating material properties and mineral identification.