Örebroite
Chemical formula: Mn²⁺₆(Sb⁵⁺Fe³⁺)(SiO₄)₂O₆
A rare, reddish-brown mineral from the humite group, found in manganese skarns in Sweden, distinguished by its association with other manganese minerals.
Properties
- Mohs hardness
- 4
- Color
- dark brown, red brown
- Luster
- Vitreous
- Streak
- reddish brown
- Density
- 0
- Cleavage
- Imperfect on {010}
- Fracture
- Irregular/Uneven
- Transparency
- Opaque
- Crystal system
- Trigonal
Diagnostic features
## Identification Örebroite is identified by its characteristic reddish-brown color, vitreous luster, and reddish-brown streak. However, the key factors are its occurrence location (mines in the Bergslagen region of Sweden) and its association with other manganese minerals, such as tephroite, sonolite, or hausmannite. ## Distinguishing from Similar Minerals It can be confused with other reddish-brown minerals from manganese skarns, such as tephroite or sonolite. Final differentiation requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS/WDS), due to visual similarity and occurrence as fine grains. ## Crystal Forms Crystals are rare and poorly developed, with a short-prismatic habit. Most often, it occurs as grains or granular aggregates embedded in the host rock (matrix).
Geological environment
## Genesis Örebroite is a metamorphic mineral. It forms as a result of contact metamorphism within iron and manganese ore deposits, in a specific geological environment known as skarns. Its crystallization occurs under high-temperature conditions, in the presence of manganese, silicon, and antimony compounds. ## Mineral Associations This mineral co-occurs with a rich assemblage of other manganese minerals and silicates. It is most commonly associated with: tephroite, sonolite, hausmannite, magnetite, katoptrite, manganostibite, magnussonite, phlogopite, calcite, and barite. ## Localities Örebroite is an extremely rare mineral, and its occurrence has been confirmed in only a few localities worldwide, all located in the Bergslagen mining region of Sweden. The main sites are the Sjögruvan mine (type locality) near Grythyttan and the Långban mine in Filipstad Municipality.
Rarity
Very rare
For collectors
## Quality Criteria The quality of an örebroite specimen is primarily assessed based on the richness of aggregates and the size of the grains. The most valued specimens are those where the mineral grains are clearly visible, well-formed, and contrast with a light rock matrix, e.g., with calcite. The presence of rare associated minerals is also important. ## Popular Localities The only source of collector specimens are the historical mines in Sweden: Sjögruvan and Långban. Specimens from these localities are highly sought after by collectors specializing in mineral systematics and rare species.
Care and storage
## Cleaning It is recommended to clean only with a soft brush to remove dust. Avoid water and any chemical agents, as the mineral often occurs on a sensitive rock matrix. ## What to Avoid Avoid contact with acids and other chemicals. The mineral is stable, but it should be protected from ultrasound and sudden temperature changes. It should not be exposed to prolonged strong sunlight. ## Storage Örebroite specimens, being microscopic and fragile, should be stored in sealed "micromount" boxes, protecting them from dust and mechanical damage. It is best to keep them in stable room conditions, away from moisture.