For those wondering about my education. Formally a high school graduate, some college. Informally though I have a nearly photographic memory for things that I read. Varied interest, access to the infinite source of information available through the internet, and a whole lot of reading about a lot of things.
I know from the past that pure gold is one of the softest metals. Through previous knowlege of metals, minerals, and their hardness I have a decent understanding of the rockwell and mohs hardness scales. Thought it best to give you a frame of reference for how easy gold is to scratch and my first thought was pure aluminum, but who has a block of pure aluminum laying around? Then I saw something about the fingernail, that one was new to me.
Titianium nitride I originally looked into after reading something about some new super-hardest ceramic material where they brought up Titainum nitride which I looked into more.
And RJ, gold is far from the softest metal. Plenty of them are malleable by hand, but gold is the most malleable metal.