Millerite thumbnail mineral, Iowa.
Millerite is a sulfide mineral composed of nickel sulfide, with the chemical formula NiS. It belongs to the hexagonal crystal system and typically forms slender, needle-like crystals. These crystals are often grouped together in radial or sheaf-like aggregates, creating visually distinctive and delicate structures.
Thumbnail specimens of millerite are small-sized samples that showcase the unique and intricate needle-like crystals of this mineral. Measuring just a few centimeters in size, these specimens are highly valued by mineral collectors for their aesthetic appeal and the rarity of well-formed millerite crystals. The color of millerite can range from brass-yellow to a brassy brown, and its metallic luster adds to its visual allure.
Millerite is commonly found in association with other sulfide minerals, often in hydrothermal veins, as well as in some sedimentary rocks. It forms under a range of geological conditions, including in serpentine deposits and in areas where hydrothermal activity has occurred.
Despite its captivating appearance, millerite can be sensitive to oxidation, which can alter its color and luster over time. As a nickel sulfide, it has been a source of nickel ore in some mining operations. However, due to its relative rarity and the fragile nature of its crystals, millerite is more commonly appreciated as a mineral specimen by collectors.
The small size of millerite thumbnails makes them convenient for display in mineral collections, allowing enthusiasts to appreciate the intricate beauty of these needle-like crystals. Care should be taken when handling these specimens to avoid damage to the delicate structures.