Eveite
Chemical formula: Mn<sup>2+</sup><sub>2</sub>As<sup>5+</sup>O<sub>4</sub>(OH)
A rare manganese arsenate, forming spherical or radial aggregates with a vitreous luster and greenish colors.
Properties
- Mohs hardness
- 3.5-4
- Luster
- Vitreous
- Streak
- White
- Density
- 3.99-4.14
- Cleavage
- Good on {101}, poor on {010}
- Fracture
- Conchoidal
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Helpful features for identifying ewite include its characteristic forms of occurrence (spherical or radial aggregates), greenish color, vitreous luster, and occurrence environment – metamorphosed manganese deposits. ## Distinguishing from Similar Minerals Ewite is visually almost identical to adamite. Certain differentiation of these two minerals requires chemical analysis (e.g., EDS) to confirm the dominance of manganese (in ewite) or zinc (in adamite). Analysis of associated minerals can be helpful – the presence of other manganese minerals (hausmannite, sarkinite) strongly suggests ewite. ## Crystal Forms It most often occurs in the form of crusts with a botryoidal, spherulitic (spherical) structure, or as radial aggregates. Very rare, well-formed crystals take the form of short prisms.
Geological environment
## Genesis Ewite is a secondary mineral, formed in the oxidation zones of metamorphosed hydrothermal iron and manganese ore deposits. ## Mineral Associations It most often co-occurs with other arsenates and manganese oxides, such as sarkinite, magnussonite, hausmannite, and braunite. Calcite and barite also accompany it. ## Localities The type locality and source of the best ewite specimens is the historic Långban mine in the Värmland region of Sweden. This mineral has also been found in Sterling Hill, New Jersey (USA), and, in small quantities, in the Tsumeb mine in Namibia.
Rarity
Very rare
For collectors
## Quality Criteria The most highly valued ewite specimens are characterized by an intense, apple-green color, good luster, and well-formed spherical aggregates. Attractiveness is enhanced by placement on a contrasting rock matrix and the presence of rare associated minerals. Due to its rarity, even small but well-formed specimens are sought after. ## Popular Localities By far the most desirable and classic specimens come from the Långban mine in Sweden. They serve as the standard for this mineral and command the highest prices in the collector's market.
Care and storage
## Cleaning Ewite specimens should be cleaned very carefully, using a soft brush and distilled water. Due to its fragility and relatively low hardness, ultrasonic cleaners and mechanical cleaning are not recommended. ## What to Avoid As an arsenate, ewite is a potentially toxic mineral. Avoid inhaling dust and wash hands after each contact with the specimen. The mineral is sensitive to acids. It should be protected from scratching by harder minerals and from sudden temperature changes. ## Storage It is recommended to store ewite specimens in separate, closed display boxes, which protects them from mechanical damage and dust accumulation. The label should include a warning about arsenic content.