??Secondly, EDXRF (X-ray fluorescent analysis instrument) measured the sample. In the result, only common composition of zoisite was detected on the table facet, while Co was detected on the pavilion facets (figure 5). This means that the coating treatment covers only the pavilion facets with a layer containing Co as a colouring agent.

fig-5: EDXRF analysis results on pavilion facets of the coated zoisite; cobalt (Co) is detected

??LA-ICP-MS (laser ablation-inductively coupled plasma-mass spectrometry) analysis on the material was also reported in the paper of McClure and Shen (2008), which stated that elements such as Zn, Sn or Pb were detected beside Co mentioned above. GAAJ-ZENHOKYO Laboratory performed further detailed analysis with LA-ICP-MS, which detected elements such as Ni, Cu or Au in high contents next to Co, other than the elements mentioned above in the report of McClure and Shen (2008) (figure 6).

fig-6: LA-ICP-MS analysis results on pavilion facets of the coated zoisite

??Durability of the coating was reviewed in the report of McClure and Shen (2008). It specifies that they were unable to scratch the coating with a pin but a knife of hardened chrome steel could make a scratch. The sample we obtained did not show peeling by wiping off with alcohol or ultrasonic cleaning, but it was confirmed that flaws were caused to the coating layer when scratched by a blade of metal such as a cutter knife.
??From the results above, analysis by GAAJ-ZENHOKYO Laboratory corresponded to the observation by AGTA-GTC and GIA previously presented. The coating treatment itself is not a new one, but zoisite dealers should be alerted to the possibility of the coated material coming into circulation in the Japanese gem market in the near future.