What Is the Mohs Scale of Hardness?
The Mohs scale of hardness is a qualitative scale used to measure the scratch resistance of a mineral. It ranks ten common minerals on a scale from 1 (softest) to 10 (hardest). The scale was created in 1812 by German geologist and mineralogist Friedrich Mohs and is a simple method for mineral identification.
Section 2: How the Mohs Scale Works
The principle behind the Mohs scale is that a harder material will scratch a softer material. For example, a mineral that can be scratched by quartz (hardness 7) but not by feldspar (hardness 6) would have a hardness between 6 and 7. It is important to note that the scale is ordinal, not linear; the difference in absolute hardness between 9 (Corundum) and 10 (Diamond) is much greater than between 1 (Talc) and 2 (Gypsum).
Section 3: A Practical Example of the Scale
The ten reference minerals on the Mohs scale are: 1. Talc, 2. Gypsum, 3. Calcite, 4. Fluorite, 5. Apatite, 6. Orthoclase Feldspar, 7. Quartz, 8. Topaz, 9. Corundum, and 10. Diamond. Geologists often use common objects for a quick field test: a fingernail has a hardness of about 2.5, a copper penny is about 3.5, and a steel nail is about 5.5.
Section 4: Importance in Mineral Identification
The Mohs scale is a valuable tool for geologists, gemologists, and rock collectors because it provides a quick, easy, and inexpensive way to help identify minerals in the field. By performing a simple scratch test, one can narrow down the possibilities of an unknown mineral sample, making it a fundamental first step in the identification process.