Good day!
Diamond is the hardest mineral in nature. But how to relate concepts such as hardness, strength and fragility? What if I say the diamond is quite fragile? This means that when the critical pressure is reached, cracks propagate in it with a striking speed, about 15 meters per second!
If diamond is the hardest mineral, does that mean it cannot be broken? Unfortunately, this is not so. The fact is that in different directions of the crystal, its hardness is not the same. This property is precisely the basis of its cutting, grinding and sawing.
Therefore, the strength of a diamond is not high; it can split into pieces from a strong impact. This somewhat limits its application. Its high hardness gives it high wear and abrasion resistance, but does not guarantee that the diamond will not break.
The concept of hardness and its measurement has long been a rather controversial issue. For a very long time they could not develop a methodology by which it would be possible to determine the amount of this parameter. Until Moos came up with the idea of measuring this parameter by trying to scratch one mineral with other minerals. If one of them was scratched by the others, then it was automatically assigned a lower hardness value. Taking a standard for each unit, he developed his own scale of hardness with indicators from 1 to 10.
Now that we have understood the concepts, we can understand how a diamond without inclusions differs from a salt and pepper diamond. Salt and pepper diamonds that are not uniform in structure are also resistant to abrasion and will just as easily scratch the glass. But due to the heterogeneous structure, they can be more fragile than pure diamonds, while remaining harder than emeralds, rubies and sapphires.
