Abstract: Recently, an orange-red tridacna variety appeared in the market.Representative orange-red tridacna samples were selected and a series of systematic gemmological tests and spectral analysis were carried out. The morphological characteristics of the gemstones were observed by microscope, the species composition of samples was tested by infrared spectrometer, and the colour genesis was analyzed by micro-laser Raman spectrometer. The results were compared with those of "golden tridacna" samples which are relatively common in the market. It was found that the infrared spectral peak of orange-red tridacna is consistent with that of tridacna. The characteristic peaks of armanite and pigment related peaks at 1 130 cm^-1 and 1 520 cm^-1 were measured by Raman spectrometer. Compared with the white part of the orange-red tridacna samples, it was found that the colour genesis is mainly related to natural organic pigment carotene, which belongs to natural colour genesis.