Deposits/occurrences of cryptocrystalline magnesite were geologically mapped and evaluated in the territory of the company CALMAG north of the town Tavsanli (District Kütahya, Western Turkey). The magnesite occurs within the Mesozoic North Anatolian Ophiolite Belt whose oceanic crustal relics were obducted onto the Anatolide-Tauride platform during the Late Cretaceous. In the northwest the ophiolite is thrusted by the Sakarya Terrane. Commercially magnesite deposits/occurrences are controlled by E-W striking fault zones. Magnesite occurs as veins within dominant shear zones respectively within extensional domains related to the shear zones or as network mineralisations (veinlets up to 10cm). The veins are massive and up to some meters thick, brecciated or in form of cauliflower concretions inside of cataclasites. Secondarily sediment hosted magnesite occurs also within strongly weathered serpentinite or at the margin of clastic sedimentary basins. These thin layers and concretions of cryptocrystalline magnesite are without economic importance. The host rock of the magnesite is mainly serpentinite, low grade metamorphosed peridotite and pyroxenite. Microgabbros occur as veins. The areas around Henry, Erna-Foral-Ambarli, Dedeler Tepe-Körkuyu, Sakislik- Dogusakislik, Kurtini-Küllüklü and Aynalicesme-Tilkiini have been mapped in detail, in order to correlate/follow the tectonic relationships/extensions of the individual mineralised zones. Due to this investigations recommendations concerning the future exploration and mine design have been made. The areas around Cem, Aksu Alti, Elmaliyurt and Baykal have been evaluated as economically interesting domains in near future.