Geologija (Dec 2011)
Characterisation of presumed meteorite from Trbovlje
Abstract
The main objective of this study was to identify and characterise a specimen of presumed meteorite, supposedly found in 1947 while crushing gangue material from an open-pit coal mining site in Trbovlje. The presumed meteorite was characterised according to its physical properties, chemical and mineral composition using EDSanalysis. Based on macroscopic characteristics and physical properties, such as external features, magnetism and density, and reaction with diluted HCl, it was established that the specimen is not a meteorite but a concretion that contains calcite. SEM/EDS analysis showed that the studied material was compositionally homogeneous. It consists predominantly of calcite, gypsum and iron sulphide. The prevailing mineral is calcite, which forms irregular grains.Iron sulphide occurs as pyrite (or marcasite), which forms thin coatings rimming calcite grains, while gypsum formsthin transitional layers between calcite grains and pyrite or marcasite crusts as a result of reaction between ironsulphide oxidation products and calcite. The matrix between grains mostly consists of very fine-grained mixture of iron sulphide, calcite, gypsum and iron sulphide oxidation products, however, fields of pure gypsum were also found between some grains. According to the composition of the concretion, it can be assumed that the specimen isa pyrite- and/or marcasite- carbonate concretion, perhaps coal ball, which most probably formed by mineralisation within peat in the early stage of coal genesis in the Trbovlje formation.
