BET method is based on the absorption of some specific molecular species in a gaseous state based on their surface. This method is used to measure physical absorption which can be used for analyzing the structure of porous materials. BET data show the geometrical shape of porosity, absorption and porosity type, volume, and size of specific surface area. The instrumental methods show that the exact contents of fluids (gas or liquid) can be absorbed by the porous material surface, at different pressures, in different materials such as gemstones. BET method is used to measure physical absorption and analyzing the structure of low-grade Neyshabour turquoise as a base for their chemical treatment. The low-grade turquoises were deposited as gangue for centuries in the area. The treatment of low-grade turquoise provides a good economic opportunity to upgrade the gemological industry in the area. This research would provide a useful framework for further steps such as finding the best turquoise for treatment as well as identifying treated samples from other turquoise sources. The result of the analysis in this research shows that the geometrical shape of porosity is two sided and from an open cylindrical type. The porosity is mainly micro-pore type (p 0≤ 0.5) and the absorption grade as high type. As a result, liquids could penetrate the low-grade turquoise rock pieces and make it possible to consider the low-grade types for further chemical treatment studies.