Mawsonite
Chemical formula: Cu<sup>1+</sup><sub>6</sub>Fe<sup>3+</sup><sub>2</sub>Sn<sup>4+</sup>S<sup>2-</sup><sub>8</sub>
A rare copper, iron, and tin sulfide, characterized by a metallic luster and reddish-brown color, often with purple iridescence.
Description
## Characteristics Mawsonite is a sulfide mineral, chemically classified as a copper, iron, and tin sulfide. It rarely forms visible crystals, most often occurring as massive, granular aggregates or as small inclusions and veinlets intergrown with other minerals, especially bornite and chalcopyrite. Its most characteristic features are a metallic luster and a reddish-brown color on a fresh surface, which quickly develops a purple-red, iridescent patina when exposed to air. ## Physical Properties This mineral is opaque and relatively soft, with a Mohs hardness of 3.5-4. It has a black streak and a significant density, reaching approximately 4.65 g/cm³. It does not exhibit cleavage, and its fracture is uneven to subconchoidal. ## Colors and Varieties The dominant color of mawsonite is reddish-brown. On weathered surfaces or upon contact with air, a characteristic, colorful iridescence in shades of purple and red quickly appears. No named varieties are distinguished. ## History and Name The mineral was first described in 1965 by N. L. Markham and L. J. Lawrence. Its name honors Sir Douglas Mawson (1882–1958), an Australian geologist and Antarctic explorer, who made significant contributions to the understanding of Australian geology. ## Applications Due to its rarity, mawsonite has no industrial applications. It is solely an object of interest for collectors and scientists studying ore deposits.
Diagnostic features
## Identification Key diagnostic features of mawsonite include its reddish-brown color, metallic luster, black streak, and high density. Its occurrence as inclusions and intergrowths with other copper sulfides, mainly bornite, is also characteristic. ## Distinguishing from Similar Minerals Mawsonite can be confused with bornite, which, however, has a coppery-brown color on a fresh fracture and more quickly develops a blue-violet patina. It can also be mistaken for nickeline, which has a lighter, more pinkish hue. Definitive identification, especially for fine-grained aggregates, often requires advanced analytical methods such as ore microscopy or chemical analysis (EDS). ## Crystal Forms Mawsonite practically does not form well-developed crystals. It occurs almost exclusively as anhedral grains, massive aggregates, and small, irregular inclusions in other minerals.
Geological environment
## Genesis It is a hydrothermal mineral, typical of some tin and copper deposits. It forms as a primary ore component in hydrothermal veins, often in close association with other sulfides. ## Mineral Associations It most commonly co-occurs with bornite, chalcopyrite, stannite, tennantite, enargite, luzonite, covellite, chalcocite, and pyrite. Its presence is often an indicator of specific chemical conditions during mineralization. ## Localities The most important localities worldwide include the Mount Lyell mines in Tasmania (Australia), which is the type locality. Significant specimens also come from the Trixie mine in Utah (USA), the Lepanto deposit in the Philippines, the Candelaria mine in Peru, as well as from some deposits in Bolivia (Oploca) and Japan.
Rarity
Rare
Collector aspects
## Quality Criteria The collector's value of a specimen is primarily determined by the richness and visibility of mawsonite within the rock matrix. Samples in which the reddish-brown parts of the mineral form distinct, large aggregates are most prized. An additional advantage is an aesthetic combination with other well-formed associated minerals, such as quartz or pyrite. ## Popular Localities Collectors particularly seek specimens from the type locality – Mount Lyell in Tasmania (Australia). Mawsonite-rich samples from the Trixie mine in Utah (USA), which yielded some of the highest quality specimens of this mineral, are also highly valued.
Care and storage
## Cleaning Dry cleaning with a soft brush is recommended to remove dust. Contact with water, especially tap water, can accelerate the oxidation and tarnishing process. If water is necessary, use distilled water and immediately dry the specimen thoroughly. ## What to Avoid Avoid contact with chemicals, acids, and detergents. Mawsonite, as a sulfide, is sensitive to humid air, which accelerates its oxidation and patina formation. It should not be exposed to prolonged strong light or sudden temperature changes. ## Storage Mawsonite specimens are best stored in a dry place, in sealed containers or display cases with controlled humidity (e.g., using desiccants). Isolation from air slows down oxidation processes and helps preserve the mineral's natural appearance.