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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Saurabh 1
Hardest silicate mineral(on mohs hardness scale) is topaz, and it's hardness is 8. While the softest silicate mineral is talc, and it's hardness is 1. So absolute difference between hardest silicate mineral and softest silicate minerals in mohs scale of hardness = 8-1 = 7. So answer is 7.