Making Grimstone Ore Unique

I propose that Grimstone variations of Iron, Lapis Lazuli, Redstone, Gold and Diamond Ore should work a little different to their Stone counterparts.

Instead of dropping the Ore directly - I think Grimstone Ore dropping "Ore Fragments" could be interesting. These would then need to be smelted down to obtain the Ore inside.

For example -

Mining regular "Stone Diamond Ore" provides a Diamond.
Mining Grimstone Diamond Ore could instead provide 1-2 Diamond Ore Fragments
Smelting these Fragments could net you a Diamond per Fragment.

This could also be affected by Fortune. Fortune III could get you anywhere between 1 and 6 Diamond Fragments. This would obviously be adjusted for Lapis Lazuli and Redstone.

This gives a reward to mining deeper but still requires a little extra input.

This idea stems from the assumption that Grimstone is harder than Stone and excavation of Ores from Grimstone could be a little more challenging than from Stone. As well as the idea that their is a higher frequency of Ore in deeper areas of the world.