Ruby

 
Color : Varying red  
Color of streak: White

Mohs’ hardness : 9
Specific gravity : 3.97-4.05   
Cleavage : None 

Fracture: Small conchoidal, uneven, splintery, brittle 
Crystal system : Trigonal
Chemical composition : Aluminium oxide
Refractive index : 1.766-1.774 
Double refraction : -0.008
Fluorescence : Strong ; ruby – red

Ruby is thus named because of its red color (Latin Rubeus). It was not until about 1800 that ruby, as well as sapphire, was recognized as belonging to the corundum group. Before that red spinel and garnet were also designated as ruby.  The coloring pigment is chrome 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 distribution of color is often uneven, in stripes or spots. As a rough stones, ruby appears dull and greasy but, when cut, the luster can approach that of diamond.