Which is the softest mineral that has been given the lowest rating of 1 on Mohs scale of mineral hardness?

The softest mineral is talc used for making the talcum powder. German mineralogist Friedrich Mohs arranged different minerals in terms of their hardness and compiled a representative scale in 1812 which is given in the accompanying table.

The hardness of a mineral was determined by its capability make scratch on another mineral. Every mineral given in the table is capable of making scratches on the others mentioned above it whereas it can be scratched by those mentioned beneath it. Although Mohs arranged minerals in one to ten sequential scale it is not regular, i.e. it does not show hardness of minerals on the same proportional scale. For example, diamond is only one stage above corundum in Mohs’ scale but actually it is 42 times harder.

If substances other than minerals are to be rated on Mohs’ scale, fingernail’s hardness is 2, knife blade’s hardness is 5 and steel file’s hardness 5.5.

Additional reading:
Friedrich Mohs (Wikipedia)
Mohs scale of mineral hardness (Wikipedia)

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