Stenhuggarite
Chemical formula: CaFe<sup>3+</sup>Sb<sup>3+</sup>As<sup>3+</sup><sub>2</sub>O<sub>7</sub>
Stenhuggarite is a very rare calcium iron arsenate-antimonate, forming tiny, dark red to black crystals with a metallic luster.
Properties
- Mohs hardness
- 4
- Luster
- Metallic, Sub-Metallic
- Streak
- Red-brown
- Density
- 5.55
- Cleavage
- Good on {001}
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Tetragonal
Diagnostic features
## Identification Amateur identification of stenhuggarite is practically impossible. The mineral is distinguished by its reddish-brown streak, metallic luster, and high density. It occurs as very fine, black or dark red crystals. Definitive identification requires specialized analyses, such as X-ray diffraction (XRD) and chemical analysis (EDS/WDS). ## Distinguishing from Similar Minerals It can be confused with other rare, dark minerals from Långban, such as magnussonite or hematophanite. Differentiation is based on chemical composition analysis (presence of calcium, iron, antimony, and arsenic in specific proportions) and crystallographic data. ## Crystal Forms It forms very small, tabular crystals with a square or octagonal cross-section, often flattened. It also occurs as granular aggregates and irregular grains embedded in the host rock.
Geological environment
## Genesis Stenhuggarite forms as a result of metamorphic processes in iron and manganese ore deposits. Its occurrence is associated with skarns and metamorphosed carbonate rocks. It forms under specific physicochemical conditions, which explains its extreme rarity. ## Mineral Associations This mineral co-occurs with other rare minerals from the Långban deposit, such as calcite, hausmannite, magnussonite, tegengrenite, hematophanite, berzeliite, and iron oxides. ## Localities The only confirmed locality of stenhuggarite in the world is its type locality – the Långban mine in Filipstad Municipality, Värmland region, Sweden. This is one of the most famous mineralogical sites in the world.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of a stenhuggarite specimen primarily depends on the presence of well-formed, even microscopic, crystals. The most valued specimens are those where crystals are clearly visible, have a defined shape, and contrast with the rock matrix. Due to its extreme rarity, every authentic specimen, even in the form of small grains, has great scientific and collector value. ## Popular Localities All known and valued specimens come exclusively from one place in the world: the Långban mine in Sweden. Specimens from this locality are unique and represent a classic for advanced collectors specializing in rare or systematic minerals.
Care and storage
## Cleaning Stenhuggarite specimens are usually very small and embedded in a rock matrix. Due to their brittleness and rarity, mechanical cleaning by amateurs is not recommended. If necessary, compressed air can be used to remove dust. Contact with water and chemicals should be avoided. ## What to Avoid All acids and strong bases, which can damage the mineral, must be strictly avoided. It is sensitive to shocks and impacts, so it should be handled with great care. It should not be heated or subjected to ultrasound. ## Storage Specimens should be stored in stable conditions, away from moisture and chemical contaminants. It is best to keep them in a sealed "micromount" box, which protects against dust and mechanical damage.