TOW (& Answer)...

The question was what mineral falls at the softest end of the Mohs scratch hardness scale?  Talc (is the answer).  It has a measure of 1 on that scale and can be scratched with a fingernail.

The question (& answer) are taken from p. 19 of Gemstones of the World by Walter Schumann.  The book was published by Sterling Publishing Co. in 1998.