The Softest Mineral
I guess the honor for the softest crystal will have to go to the mineral talc, which has a hardness of one (1) on the Mohs Hardness Scale. Talc is a silicate (like many of the earth''s most important minerals), and contains magnesium and a bit of water along with the silica and oxygen. Talc is usually associated with metamorphic rocks, and while it is pretty common in nature it is actually rather rare in crystal form.