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| Diamond, the hardest substance |
Hardness is the quality of a solid substance which enables it to scratch or resist being scratched by another substance. For instance, glass will scratch copper, therefore it is harder than copper. The degree of hardness of iron, steel and some other substances is affected by heating and cooling them. Talc is the softest and diamond the hardest substance. In the following list the substances are arranged in the order of their hardness.
1. Talc
2. Gypsum
3. Calcite
4. Fluorpor
5. Apatite
6. Feldspar
7. Quartz
8. Topaz
9. Sapphire
10. Diamond
