A key-diagram for optical routine investigation of platinum-group minerals has, for the first time, been developed on the basis of the most recent reflectance and microhardness data. The diagram contains 65 minerals, which occupy defined fields. The dominating platinum metal present in the respective minerals has been characterized by giving eachPGE a special colour. In addition, cubic (isotropic) minerals can be distinguished. The most important aspects of spectral reflectance have also been summarized.