Arsenoveszelyite

Chemical formula: Cu₂+₂Zn₂+(As₅+O₄)(OH)₃·₂H₂O

Arsenowesselyite is a rare, hydrated copper and zinc arsenate, forming characteristic blue-green, prismatic crystals.

## Characteristics Arsenowesselyite is the arsenate analogue of wesselyite, belonging to the group of secondary minerals. It forms small but well-formed, short prismatic crystals, which often occur as druses and crusts on the host rock. Its most characteristic feature is its intense, vivid color, ranging from blue, through turquoise, to blue-green. Specimens are usually small, and individual crystals rarely exceed a few millimeters in length, making it a prized micromount mineral. ## Physical Properties This mineral is characterized by a vitreous luster and is transparent to translucent. Its Mohs hardness is 3.5-4, making it relatively soft and susceptible to scratching. The density is estimated at approximately 3.6 g/cm³. ## Colors and Varieties The dominant and sole color palette of arsenowesselyite consists of shades of blue and green. The color is uniform and results directly from the presence of copper ions in the crystal structure. No color or commercial varieties are distinguished. ## History and Name The mineral's name refers to its chemical composition - "arseno" refers to the dominant arsenate anion (AsO₄) - and to its structural similarity to wesselyite, which is its phosphate counterpart. It was officially recognized as a new mineral species by the International Mineralogical Association (IMA) in 2003. ## Uses Arsenowesselyite has no industrial application. Its significance is purely scientific and collectible, being a sought-after acquisition for advanced collectors of rare minerals.

Properties

Mohs hardness: 3.5-4
Luster: Vitreous
Streak: Light blue
Density: 3.6
Cleavage: Perfect on {001}
Fracture: Conchoidal
Transparency: Transparent to Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Key diagnostic features of arsenowesselyite are its intense blue-green color, short prismatic crystal habit forming druses, and specific occurrence environment - oxidation zones of polymetallic deposits. Vitreous luster and a pale blue streak are also helpful in identification. ## Distinguishing from Similar Minerals Arsenowesselyite is sometimes confused with its phosphate analogue, wesselyite. Distinguishing between the two minerals based on visual characteristics is very difficult and usually requires chemical analysis (EDS). It can also be confused with azurite, which, however, reacts violently with hydrochloric acid and forms different crystal habits. Chrysocolla, although similar in color, is amorphous and has a lower hardness. ## Crystal Habits Arsenowesselyite crystals are most often short, prismatic with a nearly square cross-section. They usually form dense aggregates, crusts, and druses, in which individual crystals are strongly intergrown.

Geological environment

## Genesis Arsenowesselyite is a secondary mineral, formed in the oxidation (weathering) zones of polymetallic ore deposits. It crystallizes as a result of the slow percolation of solutions rich in copper, zinc, and arsenic through fractured rocks. ## Mineral Associations It most often co-occurs with other secondary minerals, such as malachite, hemimorphite, smithsonite, quartz, and especially with its phosphate counterpart - wesselyite. ## Localities The type locality, from which this mineral was first described, is located in the Vrančice area near Příbram in the Czech Republic. The most known and valued specimens by collectors, forming beautifully developed crystals, come from the historic Arakawa mine in Akita Prefecture, Japan.

Rarity

Very rare

For collectors

## Quality Criteria The collector's value of a specimen is primarily determined by the quality of crystal development - their sharpness, luster, and size. Druses with clearly separated, transparent crystals of intense, blue color are most highly prized. The aesthetic composition with associated minerals and contrasting host rock is also important. ## Popular Localities Specimens from the Arakawa mine in Japan are by far the most sought after on the collector's market. They are characterized by the best development and largest crystals of this mineral.

Care and storage

## Cleaning Arsenowesselyite specimens should be cleaned with the utmost care, using only a soft brush to remove dust. In case of heavier soiling, very gentle wiping with a cotton swab moistened with distilled water is permissible, followed by thorough drying. Ultrasonic cleaners should be avoided, as they can irreversibly damage delicate crystals. ## What to Avoid The mineral is sensitive to acids and other chemicals. It should be protected from sudden temperature changes and prolonged exposure to direct sunlight, which can cause it to fade. Due to its relatively low hardness, it is susceptible to scratches and mechanical damage. ## Storage It is recommended to store specimens in closed, padded "micromount" boxes to protect them from dust, light, and physical damage. Display should be in stable humidity and temperature conditions, away from heat sources and vibrations.

Sources

IMA Mineral List (CNMNC)