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

Abstract

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.

Further on the Choice of Space Group for Scapolite Group Members and Genetic Considerations about the Si-Al Ordering in Their Framework Construction

“…Information on the geological setting of the two Bulgarian localities, wherefrom the scapolites for the present study were selected, are given elsewhere [1,2]. Images of scapolite from the Sluydyanka deposit are presented in Figure 1.…”

“…Scapolites from Urdini Lakes (Northwestern Rila, Bulgaria), Samurski Dol (Chepelare Region, Central Rhodopes, Bulgaria), Sluydyanka (Urals, Russia), and Madagascar (Unknown Locality) Scapolite samples from four localities were studied mainly by single crystal investigations. Details on the crystal structures of the scapolites from Bulgaria are given elsewhere [1,2].…”

“…An additional degree of uncertainty and discrepancy in the determination of the linear dependencies are introduced by the specificity and quality of the X-ray experiments and chemical analyses applied by the three groups of researchers, as well as the differences in the methodologies for solving the crystal structures [1,2,6,26,27,39].…”

“…Recently, results of crystal-chemical studies of scapolites from two Bulgarian localities-Samurski dol, Chepelare region, Central Rhodopes and Urdini lakes, Northwestern Rila-were published [1,2]. Their goal was to use modern and local analytical methods (Single-crystal X-ray diffraction analysis (SXDA), Scanning Electron Microscopy (SEM), and Energy-Dispersive Spectroscopy (EDS)) to make a more precise determination of the meionite content (Me) than those previously made for samples from these localities.…”