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

most important of which are to be found on Karancs Hill where narrow veins contain galena and sphalerite. In the Tertiary sedimentary rocks the following, minerals are to be found: finely divided glauconite in sandstone (where calcite, opal, and barite occupy veins); pyrite, marcasite, and gypsum in shales, mudstones and clays; and opalised wood remains in gravels (Fig. 41). The fire clay beds at Felsőpetény, which occur in Oligocène sedimentary rocks, supply the ceramic works at Romhány with raw-material. Coal has been extracted from the Nógrád deposits since the last century on a large scale but none of the mines is in use today (Fig. 42). Splendid specimens of marcasite, pyrite, and gypsum were to be found in a smaller coal mine, closed for some time now, at Kosd near Vác. Fig. 43 OFFRETITE (0.2 mm sph) Somos kő Outcrops of isolated domes of Pliocene-Pleistocene basalts and basaltic tuffs occur in sedimentary rocks in the Medves mountains near Salgótarján. Some time ago these were widely quarried and used for road building and general building purposes. The sulfide minerals such as pyrite and pyrrhotite which are found here