Crystal structure of scapolite from Samurski Dol, Chepelare region, Central Rhodopes, Bulgaria

Samples of scapolite from the marble quarry from the Samurski Dol locality, situated nearby Chepelare, Central Rhodopes, Bulgaria have been subjected to chemical analyses and single crystal X-ray diffraction studies. The obtained values for the meionite component (Me) range between 70 and 75. The crystal structure of the studied sample has been solved in both I4/m and P42/n space groups, traditionally assigned to scapolite members. The paper provides new insight on the choice of correct space group for description of scapolites crystal structures, with a view of the preferred positions by silicon and aluminum ions and their framework ordering.