Original paper

Mineralogical and geochemical characterization of the "bituminous" agates from Nowy Kosciol (Lower Silesia, Poland)

Dumańska-Słowik, Magdalena; Natkaniec-Nowak, Lucyna; Kotarba, Maciej J.; Sikorska, Magdalena; Rzymełka, Jan A.; Łoboda, Agata; Gaweł, Adam

Neues Jahrbuch für Mineralogie - Abhandlungen Band 184 Heft 3 (2008), p. 255 - 268

published: Apr 1, 2008

DOI: 10.1127/0077-7757/2008/0098

BibTeX file

ArtNo. ESP154018403003, Price: 29.00 €

Download preview PDF Buy as PDF

Abstract

The agates from Nowy Kościół (Lower Silesia) exhibit mainly monocentric, horizontally stratified structures often developed as typical multiradial stars. The agates occurring in this region are usually spherical, shaped with diameters from 2 to 40-70 centimetres. Most of them are brownish red, honey-black or red. The dark colour of their bands is mainly caused by the occurrence of Fe-compounds, REE-bearing minerals, Zn sulphides and organic matter. The content of the latter one is relatively low (0.15 wt%), however it is strongly dispersed within the silica matrix. It forms thin laminae or irregularly shaped drops or lenses. The composition of bitumens is dominated by asphaltenes (56 wt.%) and the contribution of remaining fractions varies between 10% (aromatic hydrocarbons), 16% (resins) and 18% (saturated hydrocarbons). The stable carbon isotope analysis (saturated hydrocarbons = −28.9‰; aromatic hydrocarbons = −28.3‰; resins = −28.6‰; asphalthenes = −28.3‰; whole organic matter = −25.9‰) revealed its algal or mixed, algal-humic origin.

Keywords

agate • organic matter • trace elements • nowy kosciol • lower silesia • poland