Babánekite
Chemical formula: Cu<sup>2+</sup><sub>3</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>2</sub>·8H<sub>2</sub>O
Babánekite is a hydrated copper arsenate, forming characteristic blue-green, spherical aggregates and radial clusters of acicular crystals.
Properties
- Mohs hardness
- 2
- Luster
- Vitreous, Pearly
- Streak
- Light green
- Density
- 3.197
- Cleavage
- Good on {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Babánekite is most easily recognized by its characteristic mode of occurrence – spherical or hemispherical aggregates with a radial internal structure. Its blue-green color and occurrence in the oxidation zones of ore deposits are also important indicators. Low hardness (2 on the Mohs scale) is another diagnostic feature. ## Distinguishing from Similar Minerals Babánekite can be confused with other secondary copper minerals such as tyrolite, olivenite, or cornetite. It differs from tyrolite by the absence of distinct cleavage and pearly luster on its cleavage planes. Olivenite usually forms more massive or fibrous aggregates with an olive-green color. Cornetite is significantly harder (4.5) and has a different crystal structure. Final differentiation often requires advanced analytical methods. ## Crystal Forms The mineral forms acicular or bladed crystals, elongated along the [001] axis, which combine into radial, spherical, or hemispherical aggregates. Less commonly, individual, well-formed prismatic crystals are found.
Geological environment
## Genesis Babánekite is a secondary mineral, forming in the oxidation (weathering) zones of polymetallic ore deposits rich in arsenic and copper. It forms as a result of surface waters acting on primary arsenical and copper minerals under conditions of low temperature and pressure. ## Mineral Associations This mineral co-occurs with other secondary arsenates, such as geminite, lindackerite, erythrite, annabergite, as well as with gypsum, quartz, and tennantite-(Zn). ## Localities The most important and type locality (localitas typica) of babánekite is the historic Rovnost mine in Jáchymov, in the Czech Ore Mountains. This is the only confirmed and thoroughly described location of this mineral in the world.
Rarity
Very rare
For collectors
## Quality Criteria The most valued by collectors are specimens with well-formed, spherical aggregates of intense, blue-green color, contrasting with a light host rock (most often quartz). The size of the spherulites and the absence of damage to the delicate, acicular crystals are also important. Specimens from the type locality (Jáchymov) are particularly sought after. ## Popular Localities The only known and confirmed source of collector specimens is the Rovnost mine in Jáchymov, Czech Republic. All specimens available on the market originate from this single location.
Care and storage
## Cleaning Babánekite specimens should be cleaned only very carefully, using a soft brush to remove dust. Due to its low hardness and delicate structure, washing with water should be avoided, as it could damage the fragile aggregates. If liquid is necessary, pure isopropyl alcohol is recommended, applied with great caution. ## What to Avoid The mineral is sensitive to acids and other chemicals. Ultrasonic cleaners should be avoided, as they could destroy the delicate crystals. Babánekite is stable under normal conditions, but it should be protected from high temperatures and direct, prolonged exposure to sunlight. ## Storage It is recommended to store specimens in closed, padded boxes or display cases to protect them from mechanical damage and dust. It should be isolated from other, harder minerals that could scratch it.