What is the Mohs Hardness Scale?
* It's a relative scale of mineral hardness, ranking 10 minerals from softest to hardest.
* Each mineral on the scale can scratch any mineral below it, but not those above it.
* The scale is based on scratch tests, meaning you use a known mineral to see if it can leave a scratch on the unknown sample.
How to use the Mohs Scale:
1. Identify your unknown mineral: Start by observing its color, shape, and other physical characteristics.
2. Gather your tools: You'll need a set of reference minerals (from the Mohs scale) and a streak plate (unglazed porcelain).
3. Test the unknown mineral:
* Scratch test: Try scratching your mineral with a known mineral from the scale. If the known mineral scratches the unknown, the unknown is softer. If the unknown scratches the known, it's harder.
* Streak test: Rub the unknown mineral on a streak plate to see the color of its powder.
4. Compare and determine hardness: Based on the results of your tests, find the closest match on the Mohs Scale. Remember, it's a relative scale, so you'll need to find a range of hardness rather than an exact match.
Example:
* You find a mineral that can be scratched by a copper penny (hardness ~3) but cannot be scratched by your fingernail (hardness ~2.5). This means your mineral has a hardness between 2.5 and 3.
* You could then compare your unknown mineral to the minerals on the Mohs scale with those hardnesses (Calcite: 3 and Gypsum: 2).
Important Notes:
* Relative scale: The Mohs scale only measures *relative* hardness, not absolute hardness.
* Not the only factor: Don't rely solely on hardness to identify minerals. Other properties like color, luster, cleavage, and crystal shape are also important.
* Care with the streak plate: Some minerals are harder than the streak plate and will scratch it.
The Mohs Hardness Scale:
1. Talc: Very soft, easily scratched by your fingernail
2. Gypsum: Can be scratched by your fingernail
3. Calcite: Can be scratched by a copper penny
4. Fluorite: Can be scratched by a steel knife
5. Apatite: Can be scratched by a steel knife, but with more effort
6. Orthoclase: Can be scratched by a steel file
7. Quartz: Can scratch glass
8. Topaz: Can be scratched by corundum
9. Corundum: Can only be scratched by diamond
10. Diamond: The hardest known natural mineral
By understanding how to use the Mohs Hardness Scale, you can enhance your ability to identify minerals and unlock the secrets of the earth's diverse geological treasures.
