Grand Lama

Answer :

The method of dividing the chessboard so that each of the four parts shall be of exactly the same size and shape, and contain one of the gems, is shown in the diagram. 
The method of shading the squares is adopted to make the shape of the pieces clear to the eye. 
Two of the pieces are shaded and two left white.

The reader may find it interesting to compare this puzzle with that of the "Weaver

Math Genius