Montana agate nodules in the rough are available in large sizes. (Stock 536) These are complete nodules usually containing black or sometimes reddish brown inclusions or manganese dendrites or moss, in a clear to blue/gray translucent chalcedony. Sizes for the Montana agate nodules, good grade and complete agate nodules are from 1-7 lbs. The unique patterns of Montana agate are well known for beautiful one of a kind jewelry. The Montana agate nodule pictured to the left weighs just over five pounds. Price listed is $7.50 per one pound. See a sample slab of Montana agate slabs.