gen-define-mineral-hardness-and-the-mohs-scale-and-give-one-shor-c747

Define mineral hardness and the Mohs scale and give one short worked example.

# Mineral Hardness and the Mohs Scale ## Definition of Mineral Hardness **Mineral hardness** is the resistance of a mineral to scratching or abrasion. It's a measure of how easily the surface of a mineral can be damaged by mechanical force. ## The Mohs Scale The **Mohs Hardness Scale** is a relative scale from 1 to 10 that ranks minerals based on their ability to scratch one another. It was developed by Friedrich Mohs in 1812. **The scale:** 1. Talc (softest) 2. Gypsum 3. Calcite 4. Fluorite 5. Apatite 6. Orthoclase feldspar 7. Quartz 8. Topaz 9. Corundum 10. Diamond (hardest) **Key principle:** A mineral can scratch any mineral with a lower number and can be scratched by any mineral with a higher number. ## Worked Example **Question:** A mineral scratches calcite but is scratched by quartz. What is its approximate hardness? **Solution:** - Calcite has hardness = 3 - Quartz has hardness = 7 - Since the mineral scratches calcite, its hardness must be > 3 - Since it's scratched by quartz, its hardness must be < 7 - Therefore, the mineral's hardness is between **3 and 7** (likely 4, 5, or 6) - This could be fluorite (4), apatite (5), or orthoclase (6)