Origin and Properties of Oltu Gemstone Coal

Abstract

This study focuses on the origin and properties of the Oltu gemstone or Oltustone. The Oltu gemstone known as ‘Black Amber’ is dull-bright black color, and is very low ash, high volatile matter, total sulfur and calorific value. Very high volatile matter content on a dry-ash free basis (66.52%) and non-agglomerating character imply that its coal rank is very low. The Oltu gemstone includes abundant organic (amorphous) matter and trace amounts of quartz and pyrite. Petrographic study indicated that pyrite and quartz generally finely disseminated the organic matter. Major and trace element data have low concentrations. The trace element concentrations fall within the range values for the most world coals, except for Bi that exceeds range values (0.1–0.5 μg/g) in most world coals. Petrographic observations on the polished briquette have shown that the gemstone was made of xylite including mainly textinite and corpohuminite, minor amounts of resinite and liptodetrinite. Mean values of random reflectance (%Rr) measurements on the textinite and corpohuminite are 0.23 and 0.30%Rr, respectively. These values indicate very low coal rank, in agreement with the volatile matter.

Keywords:

• Erzurum
• gemstone
• Oltu
• quality
• trace element
• Turkey
• xylite