The fineness and hardness of 5G gold jewelry were tested by fire assay,ICP difference method,and microscopic hardness tester.The results show that the fineness of 5G gold jewelry on the market meets the requirements of GB 11887—2012 Jewelry—Fineness of Precious Metal Alloys and Designation;the minimum hardness of the tested 5G gold jewelry is 29.2 HV,and the maximum is 120.7 HV.The hardness value of most samples is in the range of 50-80 HV.The hardness of 5G gold jewelry is mainly improved through microalloying,cold deformation,surface electroforming,and other methods,involving solid solution strengthening,precipitation strengthening,deformation strengthening,and fine-grain strengthening mechanisms.