The answer would have to be Melting Temperature. The reason being that, though colour, texture and even striations are all the way outermost physical aspects, thus can be seen, recognized and felt almost instantly, however the Melting Temperature is different because you can only acquire the definite measurement of it through a test or a series of different tests.
Mercury, Sulfur and Oxygen
A. Patient is male because there is a Y chromosome
B. 47 chromosomes
C. Down syndrome or trisomy 21
