Crystal chemical study of garnets from metamorphic rocks along the Yavuz Dere River in the Sakar region, SE Bulgaria, with emphasis on use in the abrasive industry

Tzankova, N. 2007. Crystal chemical study of garnets from metamorphic rocks along the Yavuz Dere River in the Sakar region, SE Bulgaria, with emphasis on use in the abrasive industry. – Geology and mineral resources, 4, 14-18.

Abstract. The aim of this study is to provide the preliminary data about garnets from the region of Yavuz Dere valley in Sakar Mountain for their utilization as a potential raw material for the abrasive industry. The amount of garnet in the investigated rock samples is estimated at approximately 25 wt %. The garnets occur in grains with crystallographic outlines. They are fresh, with insignificant alteration processes around the cracks or filling them. The smaller porphyroblasts are almost free of inclusions (quartz, white mica, ore mineral) in contrast to the bigger ones. The garnets are almandine rich with a high content of the pyrope component – Alm 71.60 mol%, Grs 8.60 mol%, Prp 13.97 mol%, and Sps 5.83 mol%. On the basis of ICP-AES analysis the following trace elements (in ppm) are detected in the mineral samples: P₂O₅ – 1200, SO₃ – 300, Ba – 92, Co <10, Cr – 63, Ni – 40, Sr – 36, V – 115, Zn – 108, Zr – 31. The lack of the andradite end-member and the predominant almandine composition of the studied garnets define higher microhardness then those of the quartz (1120 kg/mm²). The following characteristics are established for the studied garnets: unit cell parameter – 11.558 (3) Å, density – 4.06 (g/cm³), refractive index – 1.785.

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