They also found rhenium in gadolinite and molybdenite. The veins commonly contain tourmaline, topaz, fluorite, apatite, wolframite, molybdenite, and arsenopyrite. This operation was referred to as the Net Lake Molybdenite claims. Owing to low copper and molybdenite prices, production ceased in 2016. Copper, an impurity in molybdenite, is less soluble in ammonia. There are also some other small unmined mineral veins, such as ankerite, molybdenite and haematite. The molybdenite is associated with pyrite and quartz. The ore mainly contains molybdenite, chalcopyrite, magnetite and pyrite. Occurrence of molybdenite was the basis for the mining activities at Knaben. Multilayer molybdenite flakes are semiconductors with an indirect bandgap. Molybdenite ores are essentially the only source for rhenium. Copper is produced from chalcopyrite and molybdenum from molybdenite. Chalcopyrite and molybdenite are the dominant primary sulfides. Beginning in 1848, the resultant metallic veins were mined for gold, silver, copper, and molybdenite. Molybdenite ore is processed by flotation to give relatively pure .