In the carboniferous formation of central Bohemia, millerite is a rather frequent mineral in the cavity fillings of sideritic septaria, and in geodes and veinlets in the arkoses and other sediments. The localities are numerous : Rapice, whence millerite was first mentioned by Em. Bořický, Kladno, Jemníky, Pchery, Motyčín, Dubí, and Libušín. The last locality has furnished a specimen now in the National Museum, which on a surface of about 40x20 cm. carries a dense felt of millerite needles, some of them over 4 cm. in length. The millerite and other sulphides are constantly associated with older ankerite and earthy nacrite, frequently also with barite and whewellite crystals, which are the youngest members in the paragenesis.