Yes: not a good use for a diamond, but yes, a diamond will scratch a nail.
No
See if your finger can scratch the gold. If your finger nail can than you have pure gold. But because gold is weak like that the jewelry stores usually put other minerals to make it harder.
That would be Talc.
i think so
i think so
quartz
no it doesn't transmit disease unless if there is some virus in nail
Nail polish remover... or scratch it off... It does eventually fall off.
Paint it over a new nail polish and wipe it right away
Your nail is 2.5 so the rocks you can scratch are, Gypsum and Talc.
No. Only another diamond can scratch a diamond.