Axelite

Chemical formula: Na₁₄Cu₂+₇(As₅+O₄)₈F₂Cl₂

Axelite is a very rare copper and sodium arsenate, forming characteristic blue, spherical crystalline aggregates.

## Characteristics Axelite is an arsenate mineral distinguished by its intense blue color and unique form of occurrence. It forms almost exclusively spherical aggregates (spherulites) with a radial, fibrous arrangement of crystals. Individual crystals are extremely small, acicular or platy, which gives the aggregates a silky luster on fracture surfaces. Spherulites reach sizes of up to about 0.3 mm in diameter and often occur in groups, forming crusts on the host rock. ## Physical Properties Crystals are too small for direct hardness testing, but based on composition and structure, it can be estimated as low to medium. The mineral is characterized by a vitreous to silky luster. It is opaque, and only on thin edges can it be translucent. The density calculated from the formula and cell parameters is 4.15 g/cm³. ## Colors and Varieties Axelite occurs in a uniform, light blue to blue color. No color or commercial varieties are known. ## History and Name The mineral was discovered in fumaroles of the Tolbachik volcano in Kamchatka, Russia. It was described and approved by the International Mineralogical Association (IMA) in 2015 under number 2015-078. The name honors Axel H. Müller (born 1961), a German mineral collector and specialist in secondary minerals from the Clara mine in Germany, in recognition of his contribution to mineralogy.

Properties

Luster: Vitreous, Silky
Streak: Light blue
Density: 4.15
Cleavage: Perfect on {010}
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification The diagnostic feature of axelite is its unique form of occurrence as small, perfectly spherical, blue aggregates with a radial internal structure. Its origin is also characteristic – it occurs exclusively in volcanic exhalative products (fumaroles). ## Distinguishing from similar minerals Axelite can be confused with other blue, secondary copper minerals that form spherulites, such as cyanotrichite or shattuckite. However, cyanotrichite forms aggregates with a distinctly acicular, "plush" texture, not smooth spheres. Final differentiation from other rare copper arsenates from the same locality (e.g., ericlaxmanite, popovite) requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS). ## Crystal forms The mineral forms exclusively spherical aggregates up to 0.3 mm in diameter, composed of radially arranged, platy or acicular crystals. Single, isolated crystals are not observed.

Geological environment

## Genesis Axelite is a fumarolic mineral. It forms as a result of the sublimation of volcanic gases at high temperatures (above 600°C) in active basaltic volcano fumaroles. It crystallizes directly from the gas phase on the surface of volcanic rocks. ## Mineral associations This mineral coexists with other rare arsenates and sulfates formed under similar conditions. The most important associated minerals include: hematite, tenorite, aphthitalite, johillerite, ericlaxmanite, popovite, lammerite, urusovite, and arsmirandite. ## Localities The only confirmed locality of axelite in the world is its type locality – the Yadovitaya fumarole on the second cinder cone of the Northern Breakthrough of the Great Fissure Eruption of Tolbachik volcano in Kamchatka, Russia.

Rarity

Extremely rare

For collectors

## Quality criteria The quality of axelite specimens is assessed based on the size and number of spherulites on the rock matrix, as well as their aesthetic arrangement. The most valued specimens are those with numerous, well-formed, undamaged spherical aggregates, contrasting with the darker volcanic rock. Association with other rare minerals from this locality is also important. ## Popular localities All axelite specimens available on the collector's market come from a single location in the world – the Tolbachik volcano in Kamchatka. The material was collected during scientific expeditions, and its quantity is very limited.

Care and storage

## Cleaning Axelite specimens should be cleaned only very carefully, using compressed air to remove dust. Due to the extreme delicacy of the aggregates, any mechanical contact, including with brushes or water, is discouraged. ## What to avoid Contact with water, acids, solvents, and other chemicals that can dissolve or damage microscopic crystals must be strictly avoided. The mineral is sensitive to shock and abrasion. It should be protected from high temperatures and humidity. ## Storage Axelite specimens require storage under stable conditions, preferably in a sealed, closed "micromount" box, which protects them from dust, moisture, and mechanical damage. Exposure should be away from direct sunlight and heat sources.

Sources

IMA Mineral List (CNMNC)