Wiklundite
Chemical formula: Pb<sup>2+</sup><sub>2</sub>(Mn<sup>2+</sup>,Zn<sup>2+</sup>)<sub>3</sub>(Fe<sup>3+</sup>,Mn<sup>2+</sup>)<sub>2</sub>(Mn<sup>2+</sup>,Mg)<sub>19</sub>(As<sup>3+</sup>O<sub>3</sub>)<sub>2</sub>(Si,As<sup>5+</sup>O<sub>4</sub>)<sub>6</sub>(OH)<sub>18</sub>Cl<sub>6</sub>
Wiklundite is an extremely rare, black mineral with a adamantine luster, being a complex lead and manganese arsenate and silicate from Långban, Sweden.
Properties
- Mohs hardness
- 3
- Luster
- Adamantine
- Streak
- Brown
- Density
- 4.36
- Cleavage
- None
- Transparency
- Opaque
- Crystal system
- Trigonal
Diagnostic features
## Identification The key features for identifying wiklundite are its black color, very strong, adamantine luster, and hexagonal crystal habit. Its characteristic brown streak is also distinctive. However, certain identification requires chemical analysis (EDS) and X-ray diffraction (XRD), especially since it occurs in only one specific location in the world. ## Distinguishing from Similar Minerals Wiklundite can be confused with other black, opaque minerals with metallic or submetallic luster, such as Magnetite, Franklinite, or Jacobsite, which also occur in Långban. However, it is clearly distinguished by its adamantine (not metallic) luster, brown streak (in contrast to the black or dark brown streak of the aforementioned oxides), and characteristic hexagonal crystal form. ## Crystal Forms It forms small, tabular or prismatic crystals with a hexagonal outline, rarely exceeding 0.5 mm. They occur individually or form small, scattered aggregates on the surface of the host rock.
Geological environment
## Genesis Wiklundite is a mineral of metamorphic origin. It forms in thermally altered, manganese- and iron-rich skarn deposits. Its occurrence is limited to fissures and cavities in carbonate rocks, where it crystallized in the late stages of hydrothermal processes. ## Mineral Associations This mineral occurs in association with other minerals characteristic of the Långban deposit. It most commonly co-occurs with Calcite, Andradite, Hedyphane, Mimetite, and native Lead. ## Localities The only confirmed locality for wiklundite in the world is the mines in Långban, Filipstad Municipality, in the Värmland region of Sweden. This is its type locality and, so far, the only known one.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of a wiklundite specimen is primarily assessed based on the sharpness and development of the microcrystals. Samples with clearly visible, undamaged crystals with strong luster are most valued. The abundance of crystals on the rock matrix and aesthetic associations with other minerals, such as contrasting Calcite or well-formed Andradite, are also important. ## Popular Localities The only source of collectible wiklundite specimens is its type locality – Långban in Sweden. Specimens from this location are highly sought after by collectors specializing in rare and systematic minerals.
Care and storage
## Cleaning Wiklundite specimens should be cleaned with the utmost care, preferably using compressed air to remove dust. If necessary, a soft brush and distilled water can be used, followed by gently drying the specimen. Due to its low hardness (3 on the Mohs scale), it is very susceptible to mechanical damage. Ultrasonic cleaners should be absolutely avoided. ## What to Avoid Avoid contact with all chemicals, acids, and detergents. The mineral is sensitive to scratches, so it should not be cleaned with hard brushes or wiped with cloths. Protect from drops and impacts. As a lead and arsenic-containing mineral, basic precautions should be taken, and hands should be washed after contact with the specimen. ## Storage Wiklundite, as a mineral occurring in the form of microcrystals, should be stored in a specialized "micromount" box that protects it from dust and mechanical damage. It should be kept away from other minerals to avoid scratching. Storage in stable conditions, away from moisture and extreme temperatures, is recommended.