A novel molybdenum compound, ammonium dodecamolybdomolybdate (AMM), is described which may be used in the manufacture of molybdenum metal and molybdenum carbide powders. The molybdenum compound is a dodecaheteropoly acid salt having a Keggin-type structure wherein molybdenum resides in both the hetero as well as peripheral atomic positions. The novel compound has the general formula (NH.sub.4).sub.2Mo.sub.12MoO.sub.406H.sub.2O. Because of its low solubility, the compound can be crystallized efficiently and at a high purity from ammonium molybdate solutions.