Many historic Chartaqs in Fars province, sometimes isolated individually and sometimes with accompanying structures, are known as Sassanid fire temples. This shows use of these buildings as temples of sacred fire, as well as Their dating back to the Sassanian era. Most archaeological investigations on Chartaqs are based on indicators such as plan, the presence of the corridors around the main fireplace, the remains of the fireplaces and the presence of side platforms in the rooms. In the case of the dating of these structures, the presence of Sassanid stuccos, the presence of clay pottery pieces along with the finding of coins of this period can be considered as an indicator for the determination of the Chartaqs date. In the present study, using the XRD- X-ray diffraction analysis method-, samples of twelve Chartaqs mortar of the "Firouzabad-Farashband-Kazeroun" region in the south of Fars province was analyzed. According to the results and the statistical clustering method obtained, some former archaeological investigation results was not approved. The analysis of "Tole jangi" Chartaq mortar, known as one of the "Mehr Narseh" fire temples, as well as "Gonbade Atashkadeh" Chartaq, which is considered to be the site of the fire of "Adorian", does not support the texture of time and type of use. The research has shown that the instrumental analyzing of mortar of historical structures can be an approach to help the scientific archaeological investigations of such historical structures. The research has shown that the instrumental analyzing of mortar of historical structures can be an approach to help the scientific archaeological investigations of such historical structures.