Who devised the Mohs scale used to compare the scratch hardness of minerals?

Friedrich Mohs devised the Mohs scale used to compare the scratch hardness of minerals.

Mohs, an Austrian geologist and mineralogist, introduced the scale in 1812. It orders ten reference minerals from talc, the softest at 1, to diamond, the hardest at 10. A harder mineral scratches a softer one, making the test practical even without specialized equipment.

The scale is ordinal rather than evenly spaced. For example, corundum at 9 is not simply one unit less hard than diamond; diamond is substantially harder. This is why the Mohs scale differs from quantitative hardness measurements such as Vickers hardness.

The test remains useful in field geology, mineral identification, and gemology. However, streak, cleavage, crystal form, color, density, and chemical composition are often needed to distinguish minerals that have similar scratch hardness. Mohs himself worked with mineral collections and helped establish systematic mineral classification in the early nineteenth century.