Mohs scale of hardness
Mohs scale of hardness is named after Friedrich Mohs. The scale describes the hardness of minerals and other objects. The scale range is from one (1) to ten (10) where 1 is the softest and 10 the hardest. For example, a fingernail is 2.5 Mohs, whereas a diamond is 10.
Read more:
Gemstone guide,
Diamonds,
Pearls