Gemmological Characteristic and Cause of Colour of Serpentine from South Africa

The serpentines reported from South Africa were found in the jewelry market recently. Mineral components, structural characteristics, chemical compositions and the cause of colour of the serpentine samples from South Africa were investigated with the help of X-ray powder diffraction spectrometer (XRD), infrared spectrometer (FTIR), polarizing microscope, electron microprobe (EPMA) and ultraviolet-visible spectrophotometer (UV-Vis). In addition, mineral components of serpentine from South Africa were compared with the serpentine from Liaoning Province, China.The results show the main mineral components of serpentine from South Africa were antigorite with a small amount Of lizardite and chlorite。which is similar to the serpentine from Liaoning Province.The result of electron microprobe demonstrates that the main chemical compositions of the serpentine sample are Si,Mg.It also contains a small quantity of A1 and trace amount of Fe,Mn and SO forth.The results of UV Vis combining with EPMA show that the coloration might result from the chemical element Fe.The d-d electrons transition of Fe³⁺ causes the pale yellow colour,and the charge transfer of Fe²⁺→Fe³⁺ is the major reason for the green coloration of serpentine from South Africa.