18k vitguld. St 16/50.
The phenomenum of naturally coloured diamonds is explained by the components of atoms in the crystal stucture. A diamond is composed by perfectly combined carbon atoms making the diamond the hardest material in the world.
With the presence of nitrogen atoms replacing a carbon atom in the cubic structure the diamond appears yellow. A strong saturation of colour is more expensive and preferred to lighter colours. The presence of boron atoms would make a diamond appearing blue. The colour is due to the diamonds absorbtion of certain wave lenghts of the reflected light specta.