It is well known that the so-called "American natural turquoises" in the present market are actually mostly treated by Zachery process. By means of enlarged observation, UV-visible spectroscopy, scanning electron microscopy, X-ray fluorescence spectrometer and infrared spectrometer, the authors carried out the study of the gemology, mineralogy, chemical composition and spectral characteristics of Zachery-treated turquoise. The results showed that, due to the wide range of variation in the characteristics such as luster, structure, density and hardness of the natural turquoises, it is impossible to distinguish and identify the Zachery-treated turquoises by the conventional gemological tests and the UV - visible spectroscopy as well as infrared spectroscopy, and only the existence of the high K⁺ element content shown by X-ray fluorescence spectrometer and the observation of the crystalline phenomenon on the turquoise surface by scanning electron microscopy can be used as the accurate judgment basis of Zachery-treated turquoises.