The name diamond refers to its hardness (Greek - Adamas, unconquerable).
There is nothing comparable to its hardnesses; it is therefore nearly imperishable.
Compared to corundum, diamond's cutting resistance is 140 times greater. Although
hardness is different in the individual crystal faces. This allows diamond to be
cut by diamond (or diamond powder, in which - according to statistical probability -
various diamond harness occur). Mounting care must be taken because of perfect cleavage.
To the experienced eye, a diamond's strong luster can reveal the difference between a
real diamond and it's imitations.
Blue-green: (5370), 5040 (4980)
Brown and green: often green