posted by Anonymous .
What test is performed to determine the hardness of a mineral?
The Rockwell test is very common in laboratories http://en.wikipedia.org/wiki/Rockwell_scale
look up the MOHS Hardness scale; it consists of ten minerals ranging from the softest (#1 - talc) to the hardest (#10 - diamond)
harder minerals will scratch softer ones.
a fingernail has a hardness of about 2.5, while a penny's is 3.5