The coloring pigment is chrome,e and, for brown hues, some iron additionally. The red color varies with the individual deposits, so it is not possible to determine the source area from the color, as each deposit yields various tones. The designation “Burma ruby” or “Siam ruby” is erroneous, and refers, more to quality than origin. The most desirable color is “pigeon’s blood”, pure red with a hint of blue. The distribution of color is often uneven, in stripes or spots. As a rough stone, ruby appears dull and greasy but, when cut, the luster can approach that of diamond.
The hardest material after diamond, although only 1/140th as hard, it is seven times as hard as topaz, the nest on Mohs’ scale. However , the hardness varies different directions, a fact that is made use of by the lapisdary. Because of the great hardness, corundum which is unsuitable for jewellery purposes, is powdered and used as acutting and polishing medium.
Ruby has no cleavage, but has certain preferred of parting. Because of its brittleness, care must be taken when cutting and setting.

*Info by the book of Walter Schumann “Gemstones of the World”