Germany contains many old and classic localities for Millerite, with the best being the Friedrich Mine, Wissen, Siegerland (unusually thick crystals) and Ramsbeck, North Rhine-Westphalia. Other worldwide localities include the Glamorgan area, Wales, UK; Kladno, Bohemia, Czech Republic; the Perseverance Mine, Leinster, Leonora Shire, Western Australia; and the Pafuri Nickel Deposit, Limpopo Province, South Africa.
In the U.S., dense Millerite needles in
geodes are well-known at the Route 27 Roadcut, Halls Gap, Lincoln Co., Kentucky. Highly aesthetic
acicular sprays in
vugs with Stilpnomelane were found in the Sterling Mine, Antwerp, Jefferson Co., New York, which is another classic locality for this mineral. Thick Millerite mats in geodes come from Ollie, Keokuk Co., Iowa; and Millerite embedded inside
Calcite crystals from Keokuk, Lee Co., Iowa.
Botryoidal Millerite aggregates formed from
radial needles have come from the Gap Mine, Lancaster Co., Pennsylvania; and aesthetic sprays from Estabrook Park in the city of Milwaukee, Milwaukee Co., Wisconsin. Hairy Millerite masses have been found at the Wallace Quarry, Pigeon, Huron Co., Michigan; and tree-like formations of densely interconnected crystals create an aesthetic form of this mineral at the Meikle Mine, Elko Co., Nevada.
In Canada,
radiating Millerite balls and veins have come from the Thompson Mine, Manitoba; and
massive Millerite with
Chalcopyrite was mined in Levack Township, Sudbury, Ontario.