Comparative investigations on Gagate and Vitrain from the Balkan coal basin

Isometamorphous samples of gagate and vitrain from Balkan coal-bearing formations were investigated. Quantitative spectrophotometric, chemical and reflectance measurements were performed. The data obtained from quantitative IR-analysis indicate great differences in the functional composition and structure of the organic matter of the two coal lithotypes. This explains the different properties of the gagate, e.g. lower reflectance, high volatile matter and hydrogene contents, etc. In the case of gagate the aliphatic part predominates in a naphthenic form and hybrid structures bonded to benzene rings as hydroaromatic cycles. Therefore, the number of benzene rings is several times lower than in vitrain, the elemental composition remaining the same. This is why under identical thermobatic conditions and through geological time, the coal molecule of gagate has a lower degree of aromatization.