Tungsten Carbide tips will easily scratch a sapphire crystal.
It has a Rockwell C hardness of over 72. Although softer than a diamond it will scratch even a diamond.
The secret is how pointed is the tip that is doing the scratching. The narrower and more pointed the easier it will scratch surfaces.
The scratching happens not just from hardness, but also from the pressure. The smaller the tip the greater the pressure.
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