Szakáll Sándor - Jánosi Melinda: Minerals of Hungary (Topographia Mineralogica Hungariae 4. Miskolc, 1996)

abroad. Uranium minerals occur in lenticles embedded in sandstone strata. The actual structure of these deposits is as follows: the central zone of uraniferous sandstone is dark grey and rich in carbonised plant remains. This is surrounded by a greenish border layer which, in turn, is surrounded by an oxidised red sandstone. Primary uranium minerals (uraninite, coffinite) appear mainly as the cement of the sandstone and are often accompanied by sulfides (pyrite, galena), chromium- and vanadium-bearing illite (emerald green), and hematite. In the oxidation zone, lemon yellow, orange and occasionally green secondary uranium minerals (liebigite, zippeite, uranopilite, soddyite, and andersonite) are present, often as efflorescences, or thin crusts (Fig. 70). Larger concentrations of sulfides (galena, tetrahedrite, sphalerite, chalcopyrite, pyrite, marcasite and pyrrhotite) are usually found in the vicinity of carbonised or charred plant remains together with quartz, carbonates, and barite. Dolomite concretions containing well developed crystals of different varieties of quartz (rose, smoky and rock crystal), carbonates (calcite, siderite, dolomite), sulfides (galena, sphalerite, chalcopyrite, pyrite), sulfates (barite, gypsum, anhydrite), and rarely arsenates (picropharmacolite, talmessite), are not uncommon. Most of Triassic sedimentary rocks occur in the central part of the Mecsek and in the Villány mountains. In joints abd fractures in these rocks, calcite, dolomite and quartz are common. Limestone caves in the area are usually very poor in minerals with the exception of caves discovered in the Beremend quarry where various forms of calcite, aragonite, and huntite can be found (Fig. 71). Limestone from this quarry is used for making cement. In some Triassic limestone quarries, indications of copper were found. A particularly good example was found in the now abandoned quarry near a hunting lodge at Kozár, near Pécs which became famous for its rich mineral assemblage. Here, some eye-catching secondary copper minerals, e.g., malachite, azurite, olivenite, conichalcite, cuprite and copper, are the oxidised products of chalcopyrite, chalcocite and tennantite (Fig. 72 and 73). Coal deposits of the Jurassic around Komló and Pécs, have been mined since the end of the 18th century. The trouble with them is