Emerald and diamond ring, two-coloured gold

Color : White diamonds color range from D (colorless, the purest white) to Z (light color). D, E and F are colorless diamonds, G, H , I and J are near colorless , K and L are faint color, M to Z have a light color.
Diamond : In mineralogy, diamond is an extremely rare, precious and hard (named after the ancient Greek "unbreakable") metastable allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice.
Gold : Because of the softness of pure gold, it is alloyed with silver, copper or palladium. The proportion of these other metals give yellow, white gold. Without precision, the gold used in jewelry is 18 K, corresponding to 75% pure gold.
Brilliant cut : The modern brilliant cut was developed by Marcel Tolkowsky in 1919. It consists of 58 facets (or 57 if the culet is excluded). It is the most popular modern cut because it provides maximized light return through the top of the diamond.