Rouseite

Chemical formula: Pb₂+₂Mn₂+(As₃+O₃)₂·₂H₂O

Rouseite is a very rare lead manganese arsenite, forming tiny, orange-red crystals with a vitreous luster.

## Characteristics Rouseite is a hydrated lead manganese arsenite, occurring as very small, tabular or bladed crystals that rarely exceed 1 mm in length. It typically forms small clusters, aggregates, or coatings on host rocks. Its most characteristic feature is its intense, orange-red to reddish-brown color. ## Physical Properties Rouseite crystals exhibit a vitreous luster. This mineral is relatively soft, with a Mohs hardness of approximately 3. It is a rather dense mineral, which results from the high lead content in its chemical composition. Crystals are transparent to translucent. ## Colors and Varieties The predominant and only known color of rouseite is orange-red, transitioning to reddish-brown. No color or commercial varieties are distinguished. ## History and Name The mineral was first described in 1970 by Pete J. Dunn and Roland C. Rouse. The name comes from Roland C. Rouse (b. 1942), a crystallographer from the University of Michigan, in recognition of his contributions to the study of minerals from Långban, including the description of rouseite's crystal structure. ## Uses Rouseite has no industrial application. Due to its extreme rarity and small crystal size, it is a mineral of purely scientific and collectible importance, sought after by specialized collectors of rare minerals.

Properties

Mohs hardness: 3
Luster: Vitreous
Streak: Orange
Density: 5.33
Cleavage: Perfect on {010}
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Rouseite can be identified by its characteristic orange-red color, small, tabular crystals, and occurrence in a specific geological environment. Vitreous luster and an orange streak are also important diagnostic features. ## Distinguishing from Similar Minerals It can be confused with other rare arsenates or arsenites from Långban, such as magnussonite or finnemanite, but it differs from them in crystal habit and specific chemical composition. Accurate identification requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS). ## Crystal Forms Rouseite crystals are very small, typically tabular or bladed, elongated along one axis. They crystallize in the monoclinic system. They occur as single, isolated crystals or form small, radial aggregates on the rock surface.

Geological environment

## Genesis Rouseite is a mineral of metamorphic origin. It forms in iron and manganese ore deposits that have undergone regional or contact metamorphism. It occurs in skarns and carbonate rocks, filling small fractures and fissures. ## Mineral Associations This mineral co-occurs with other rare minerals typical of the Långban deposit, such as magnussonite, tegengrenite, finnemanite, hausmannite, baryte, calcite, and lead. ## Localities The only confirmed and classic locality for rouseite in the world is the Långban mine in Filipstad Municipality, Värmland County, Sweden. This is its type locality.

Rarity

Extremely rare

For collectors

## Quality Criteria For rouseite collectors, the most important criteria are: the presence of well-formed, sharp crystals with an intense, orange-red color. Due to their microscopic size, specimens are evaluated under magnification. Rich crystal aggregates or single, but distinctly formed crystals on a contrasting host rock background are highly prized. Association with other rare minerals from Långban is also important. ## Popular Localities The only source of rouseite specimens is the historic Långban mine in Sweden. All specimens available on the collector's market originate from this single locality and are usually fragments of old, historic collections.

Care and storage

## Cleaning Rouseite specimens should be cleaned only with extreme care, using a soft brush to remove dust. Due to its softness and potential reactivity, contact with water and any chemical agents should be avoided. ## What to Avoid Ultrasonic cleaners, chemicals, acids, and solvents must be absolutely avoided. The mineral is susceptible to mechanical damage, so it should be protected from scratches and impacts. As an arsenite, it is toxic – avoid inhaling dust and wash hands after any contact with the specimen. ## Storage Rouseite specimens are best stored in closed, padded "micromount" boxes to protect them from dust, mechanical damage, and direct contact. Store in a dry place, away from heat sources and direct sunlight.

Sources

IMA Mineral List (CNMNC)