Where did you find information on carmeltazite’s Mohs hardness? There is no hardness value given for this mineral on Mindat, nor is any listed in this 2018 paper on the mineral.
This 2019 Forbes article notes that some media have erroneously reported that the mineral is harder than diamond. On the other hand, it’s theoretical density/SG has been calculated to be greater than diamonds. This might be the source of that confusion.
Pedro
IGS Admin