Millerite is a nickel sulfide mineral encountered in several ultramafic and sedimentary environments, but like cobaltite it is rarely sold as a discrete product. Instead, it feeds into the broader nickel sulfide concentrate stream. Global nickel production has grown strongly over the last decade, with sulfide ores (including those containing millerite) complementing a rapidly expanding laterite and nickel pig iron (NPI) segment. Sulfide-derived production is prized for its relatively low impurity profile and suitability for battery-grade nickel intermediates.