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

copper is also present a rich mineral assemblage is developed accompanied by a lot of alunite, as at Legyesbénye. As a consequence of their conditions of formation they often contain opalised (silicified) plant remains (branches, trunks, seeds, pods). Internationally quoted localities are situated near Megyaszó, Arka (Fig. 15), and Boldogkőváralja, (these localities were reported in the literature as far back as the 18th century). Because of its hardness and homogeneous texture limnoquartzite was favoured by prehistoric man, who used it to make tools. Archeologists have found many of these implementmaking 'workshops' all over the mountains. Fig. 15 OPAL, wood opal (9 cm sp) Arka In this region are also found hydrothermal gold and silver ores which have been known since Medieval times and which were deposited in potassium-rich andésites, and rhyolites. The best-