The results of mineralogical studies by XRD, XRF and thin section techniques showed that the main minerals of the deposits (Bafgh-Yazd region, containing 5 – 10 percent sillimanite minerals group, with 18 – 20% Al2O3) were quartz, sillimanite, mica (biotite and muscovite), garnet, kyanite, andalusite and some opaque minerals. Mineral processing studies showed that the kyanite concentrate from this ore could be obtained by using different methods such as magnetic separation, vibrating table, and flotation. The results of experiments showed that a concentrate of 42% Al2O3 with 54% recovery was obtained by using a vibrating table. In order to separate iron-bearing minerals (Fe2O3 contents to less than 1%), the concentrate was processed by high-intensity magnetic separation. This increased the Al2O3 content to 62%. Applying the flotation method to the fine fraction of the sample (75 – 150 μm) yielded a concentrate containing 46.3% Al2O3, , with a recovery of 47.56%. The process of mullitization of kyanite concentrate was also studied under different heat-treatment conditions (1400 – 1600°C and 0.5 – 3.5 h) and with different particle sizes (38 – 300 μm). The results of microstructural and phase evolution studies by SEM and XRD showed that complete transformation of kyanite to mullite took place by means of heat treatment in the range 1500 – 1550°C over a period of 2.5 h. At 1550°C, the rates of mullitization and densification were increased as a result of a decrease in the materials’ particle size from 300 to 38 μm.