Suppose scientists have 2 substances that look alike. how could they use density to see if they are the same substance?

Density can prove many things, like the density in water and oil, oil has a different yet thicker density, they could poor it into the same bowl, if they are separated they are different density, meaning they are different substances, if they come together, they might have a thinner density. 

Gravitational force i believe

Calcinosis is the diagnostic term that means an abnormal buildup of calcium on the kneecap (patellar) surface. it is a term uses to describe a group of disorders in which calcium deposits form in the skin. it is also referred to the abnormal deposit of calcium phosphate.