Millerite is rarely seen in geodes such as this and Halls Gap in Kentucky is one of the most classic occurrences for the species in the United States. This piece hosts several, needle-thin, metallic, silvery-bronze color acicular crystals of Millerite in a geode of Calcite with Pyrite. A very good representative specimen of this rare nickel sulfide from a state that is not known for its mineral specimens. Ex. Richard Kosnar Collection.