Molybdenite. Sample of the ore molybdenite (molybdenum disulphide, MoS2), which is a soft, flaky, metallic mineral composed of elongate crystals. It is a source of molybdenum, an element widely used in all kinds of metallic alloys and products. Molybdenite is also the only source for the rare radioactive element rhenium. This specimen is 12 centimetres across.