Sahlinite

Chemical formula: Pb₂+₁₄O₉(As₅+O₄)₂Cl₄

Sahlinite is a very rare lead arsenate with a characteristic sulfur-yellow color, found mainly in the Långban deposits in Sweden.

## Characteristics Sahlinite is a complex lead arsenate, oxide, and chloride, most commonly occurring as platy, scaly, or granular aggregates. It rarely forms distinct, tabular crystals. Its most characteristic feature is its intense, sulfur-yellow to canary-yellow color, which makes it easily noticeable among other minerals. ## Physical Properties This mineral exhibits an adamantine or slightly resinous luster. It is relatively soft, with a Mohs hardness of 2.5-3, meaning it can be scratched with a copper wire. It is a very heavy mineral due to its high lead content—its density is approximately 7.8-7.9 g/cm³. It is translucent, and in thicker fragments, opaque. ## Colors and Varieties Sahlinite occurs in shades of yellow, from sulfur-yellow, through canary, to yellowish-green. No named color varieties or commercial varieties are distinguished. ## History and Name The mineral was first described in 1934 by Gustaf Flink. The name "sahlinite" was given in honor of Carl Andreas Sahlin (1861–1943), a Swedish metallurgist and director of the ironworks in Kolsva, in recognition of his contribution to Swedish industry. ## Uses Due to its extreme rarity, sahlinite has no industrial applications. It is solely an object of scientific interest and a prized acquisition for advanced systematic and regional mineral collections.

Properties

Mohs hardness: 2.5-3
Luster: Adamantine to Resinous
Streak: Pale yellow
Density: 7.8-7.9
Cleavage: Perfect on {010}
Fracture: Uneven
Transparency: Translucent to Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification A key diagnostic feature of sahlinite is its very high density, which can be felt even in a small specimen. The characteristic sulfur-yellow color, pale yellow streak, softness, and perfect cleavage in one direction are also important clues. The geological context—occurrence in skarns from Långban—is almost certain confirmation. ## Distinguishing from Similar Minerals Sahlinite can be confused with other yellow secondary lead minerals. It is distinguished from mimetite by its lower hardness and different crystal habit (mimetite forms hexagonal prisms). Wulfenite, although similar in color, crystallizes in thin, square tablets and is also slightly harder. Final differentiation requires advanced analyses, e.g., X-ray diffraction. ## Crystal Forms Sahlinite most commonly forms scaly, platy, or massive aggregates. Well-formed, single tabular crystals are extremely rare and small.

Geological environment

## Genesis Sahlinite is a secondary mineral, forming under conditions of high-temperature contact metamorphism. It originates in unique, manganese- and iron-rich skarns that have undergone subsequent hydrothermal processes. ## Mineral Associations This mineral co-occurs with other rare minerals typical of the Långban deposit, such as hedyphane, mimetite, magnetite, hausmannite, braunite, and calcite. ## Localities The most important and classic locality for sahlinite is its type locality—the Långban deposit in the Värmland region of Sweden. This is one of the most famous mineralogical sites in the world. Besides Långban, its presence has also been noted in the nearby Jakobsberg mine and in Franklin, New Jersey, USA, but specimens from these locations are even rarer.

Rarity

Very rare

For collectors

## Quality Criteria The most highly prized sahlinite specimens are those that exhibit rich, visible aggregates of the mineral with an intense, yellow color. The presence of even poorly formed crystals significantly increases value. Associations with other rare minerals from Långban, which create aesthetic and scientifically valuable samples, are also highly desirable. ## Popular Localities The only source of valuable collector specimens is the historic Långban deposit in Sweden. Specimens from this locality are classics and adorn advanced collections of rare minerals.

Care and storage

## Cleaning Sahlinite specimens should only be dry-cleaned, using a soft brush to remove dust. Due to its chemical composition and softness, contact with water and any chemical agents should be avoided. ## What to Avoid Sahlinite is a toxic mineral due to its lead and arsenic content—hands should be thoroughly washed after each contact with a specimen. It should be protected from acids and detergents. It is very soft and has perfect cleavage, making it susceptible to scratches and mechanical damage. Ultrasonic cleaning is forbidden. ## Storage It is recommended to store specimens in separate, sealed, and clearly labeled boxes (with toxicity information) to prevent dusting and accidental contact. It should be kept away from harder minerals that could scratch it.

Sources

IMA Mineral List (CNMNC)