Ericssonite
Chemical formula: BaMn<sup>2+</sup><sub>2</sub>Fe<sup>3+</sup>(Si<sub>2</sub>O<sub>7</sub>)O(OH)
Eriksonite is a rare barium, manganese, and iron silicate, forming dark, tabular crystals with a vitreous or metallic luster.
Properties
- Mohs hardness
- 4.5
- Luster
- Vitreous to Sub-Metallic
- Streak
- Red-brown
- Density
- 4.23
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Opaque, Translucent in thin fragments
- Crystal system
- Monoclinic
Diagnostic features
## Identification Characteristic features of eriksonite include its black color, tabular crystal habit, perfect cleavage in one direction, and high density. It occurs in a specific geological environment – in manganese ore deposits. ## Distinguishing from Similar Minerals Eriksonite can be confused with other dark, tabular manganese minerals, such as pyrophanite or some micas (e.g., biotite). It is distinguished from them by its higher density, specific reddish-brown hue in thin fragments, and mineral associations. Biotite is significantly lighter and more flexible. Accurate identification requires advanced methods, such as X-ray diffraction (XRD). ## Crystal Forms Crystals are typically thin- to thick-tabular, with a square or rectangular outline. They often form fan-shaped or rosette-like aggregates, where individual crystals radiate outwards from a common center.
Geological environment
## Genesis Eriksonite is a metamorphic mineral. It forms in barium- and manganese-rich oxide deposits that have undergone contact metamorphism. It occurs in skarns and hornfels formed at the contact of magmatic intrusions with manganese-rich sedimentary rocks. ## Mineral Associations This mineral coexists with other manganese and barium minerals, such as braunite, baryte, hausmannite, jacobsite, rhodochrosite, tephroite, as well as with calcite and quartz. ## Localities The most important and type locality for eriksonite is the Långban mine in the Värmland region of Sweden. It is also known from the Esquire #7 and #8 mines in Fresno County, California, USA.
Rarity
Very rare
For collectors
## Quality Criteria For collectors, the most desirable specimens are those with well-formed, sharp, tabular crystals, forming aesthetic, rosette-like aggregates. Specimens where eriksonite contrasts with a lighter rock matrix, such as white baryte or calcite, are also highly valued. Crystal size and the richness of clusters significantly increase the specimen's value. ## Popular Localities By far the most prized and classic specimens come from the type locality – the Långban mine in Sweden. Specimens from California are also sought after by collectors specializing in minerals from that region.
Care and storage
## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Brief rinsing in distilled water is permissible, followed by thorough drying. Ultrasonic cleaners should be avoided. ## What to Avoid Avoid contact with acids and other chemicals that may damage the mineral's surface. As a dark-colored mineral, it is not particularly sensitive to light, but prolonged exposure to strong sunlight is not recommended. It is brittle and susceptible to impact. ## Storage Eriksonite specimens are best stored in separate, padded collector boxes to prevent scratches and mechanical damage. It should be protected from moisture and sudden temperature changes.