A HALF-CENTURY OF ENVIRONMENTAL MINERAL FORMATION ON A PYRITE-BEARING WASTE DUMP IN THE MATRA MOUNTAINS, HUNGARY

Intensive Zn–Pb–Cu mining took place for about 40 years in the Gyongyosoroszi–Matraszentimre region, Matra Mountains, Hungary. The last mine was closed in 1986 without remediation. In 2006, a large-scale project was launched for the complete remediation of the waste dumps (more than 20 sites) and for the proper sealing of the abandoned shafts and adits still releasing acid mine-drainage owing to the large amount of oxidizing pyrite in the walls. During the remediation, full profiles (up to 5–10 m) of old dumps were created, offering a unique opportunity for the systematic sampling of the products of mine-waste alterations. One of these accessible “natural laboratories”, recording 40 years of environmental mineral formation, is the Banyaberc waste dump. Its volume reached 26,000 m 3 , and its bulk pH was around 3.7. We carried out XRD, SEM–EDX and Mossbauer spectroscopic (room temperature, liquid nitrogen) analysis of the minerals present in the altering waste-dump material. Minerals found are pyrite, gypsum, jarosite, hydroniumjarosite, plumbojarosite, anglesite, quartz, the feldspars, goethite, hematite, pickeringite, alunogen, epsomite, hexahydrite, a smectite-group phase, galena, sphalerite, and trace calcite. Rhomboclase and copiapite were identified by XRD in only one