Abstract
Untill 1993 the iron ores were presented in the Polish mineral resources data file. They are: Middle and Lower Jurassic sedimentary siderite deposits and Middle Jurassic ironbearing, limonitic sands, formed in weathering zone of sideritic sandy limestones. After economic evaluation, theywere excluded fromthe data file. The deposits that could be considered as potentially economic should contain at least 25% of Fe, and are characterized by ore accumulation over 2.5 t/m2• Polish siderite ores, although of higher iron content, are characterized by very low thickness 0.12-0.47 cm, and therefore by low ore accumulation, less then 1.5 t/m2 (-400 kg Fe/nr'), far less than the minimum acceptable as possible economic. The iron bearing, (limonitic) sands are 10-13 m thick in average, but contain only 16.6-17.6% Fe, so below the acceptable limit for economic ore. They need costly thermic processing to get the product suitable for further enrichment and metallurgical treatement. The both siderite and ironbearing sand deposits are extremly poor when compared with the iron ore deposits recently mined. It is very improbable that they can get economic value in the future and can not be classified even as subeconomic. Their elimination from the Polish mineral resources data file ends over 2000 year history of iron ore mining in Poland, which added substantial value to the national economy in the past.
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