Diaspore crystals (AlO(OH)) of worldwide gem quality are only found in Turkey. Therefore, they highlight mineralogical geosites in the discussion of geoconservation and must be considered as an important element of the geoheritage of Turkey. These crystals, which have a transparent appearance, vitreous striated outer surface, perfect cleavage, sometimes giant sizes, and V-shaped twinning, have only been extracted from one mine deposit in the southwestern Anatolia since 1972. These crystals may be named as Anatolian diaspore crystals individually. Since 2005, they have been sold under the trade name "zultanite" in the world gem market. The diaspore crystals and associated minerals in the paragenesis, such as muscovite, chloritoid, donbassite, ilmenite, and specular hematite, are also unique with regard to their origin. They were formed as remobilized secondary mineralization in fracture zones that cross-cut a karst unconformity-type diasporite ore surrounded by İlbirdaǧi marbles in the southwestern part of the Menderes massif (Milas-Muǧla region) during the Paleogene Period. The existence of Anatolian diaspore crystals is limited to only one deposit, thus constituting a geosite. This geosite is already inscribed in the list of the geological frameworks of Turkey as a result of the initiatives of the Turkish Association for the Conservation of the Geological Heritage. Nevertheless, an effective protection of this geosite is not yet implemented by the Turkish authorities. © 2010 Springer-Verlag.