Welinite

Chemical formula: Mn<sup>2+</sup><sub>6</sub>(W<sup>6+</sup>&#9744;)(SiO<sub>4</sub>)<sub>2</sub>O<sub>4</sub>(OH)<sub>2</sub>

Welinite is an extremely rare mineral from the group of manganese silicates and tungstates, known exclusively from one locality in the world – the Långban mine in Sweden.

## Characteristics Welinite is a complex manganese silicate and tungstate. It forms small, hexagonal crystals with a tabular or short-prismatic habit, rarely exceeding a millimeter in size. It most often occurs as embedded grains or granular aggregates within a calcite or skarn rock matrix. Its color is dark, ranging from reddish-brown to almost black. ## Physical Properties The mineral's hardness is approximately 4 on the Mohs scale. It exhibits a vitreous, sometimes metallic luster. It is an opaque mineral, only translucent on thin edges. Due to the presence of heavy tungsten, welinite has a high density, ranging from 4.63 to 4.71 g/cm³. ## Colors and Varieties This mineral does not show much color variability, maintaining a hue from reddish-brown to black. No varieties have been distinguished. ## History and Name It was described in 1967 by Paul B. Moore and Paul Ramdohr. The name welinite honors Eric Welin (1923–2014), a Swedish mineralogist and geologist from the Swedish Museum of Natural History in Stockholm, for his contributions to the study of Swedish minerals. The type locality and only known occurrence is the Långban mine in Sweden. ## Applications Due to its extreme rarity and occurrence as microscopic crystals, welinite has no industrial applications. It is solely an object of scientific and collector interest.

Properties

Mohs hardness
4
Luster
Vitreous to submetallic
Streak
Brownish red
Density
4.63-4.71
Cleavage
Indistinct on {0001}
Fracture
Uneven
Transparency
Translucent to opaque
Crystal system
Hexagonal

Diagnostic features

## Identification A key diagnostic feature is its origin from Långban and its co-occurrence with other rare minerals from this locality. Identification is facilitated by its high density, dark, reddish-brown color, and characteristic shape of hexagonal crystals. ## Distinguishing from Similar Minerals It can be confused with other dark minerals from Långban, such as braunite or jacobsite. Braunite is harder (approx. 6-6.5 on the Mohs scale), and jacobsite exhibits magnetic properties. Due to its rarity and similarity to other minerals from this paragenesis, definitive identification of welinite often requires advanced analytical methods, e.g., X-ray microanalysis (EDS). ## Crystal Forms It crystallizes in the hexagonal system. It forms short, prismatic or tabular crystals, often grouped into granular aggregates.

Geological environment

## Genesis It forms in iron and manganese ore deposits that have undergone contact metamorphism. It occurs in skarns and lenses of metamorphosed carbonates. ## Mineral Associations It co-occurs with a rich assemblage of minerals typical of Långban, including calcite, andradite, tephroite, richterite, karyinite, and berzeliite. ## Localities The only confirmed locality of welinite in the world is the Långban mine in the Värmland region of Sweden.

Rarity

Extremely rare

For collectors

## Quality Criteria The collector's value of welinite primarily depends on the crystal habit and size. Sharp, well-formed crystals, even if small, are highly prized. The attractiveness of a specimen is also enhanced by its placement on an aesthetic rock matrix in association with other rare minerals from Långban. ## Popular Localities All valuable specimens come from the historic, now inactive Långban mine in Sweden, which is considered one of the most important and mineralogically diverse localities in the world.

Care and storage

## Cleaning Welinite specimens should be cleaned very carefully, preferably with a soft brush when dry. If necessary, distilled water may be used, but the specimen must be thoroughly dried immediately. ## What to Avoid Avoid ultrasonic cleaners, strong chemicals, and acids. Although not particularly sensitive to light, prolonged exposure to direct sunlight is recommended to be avoided. ## Storage Store in stable conditions, protected from dust, moisture, and sudden temperature changes. It is best to place the specimen in a closed display box to prevent mechanical damage.

Sources

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