Strashimirite

Chemical formula: Cu<sup>2+</sup><sub>4</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>·2.5H<sub>2</sub>O

Strasimirite is a rare hydrated copper arsenate, forming characteristic spherical or hemispherical aggregates of an intense blue-green color.

## Characteristics Strasimirite is a secondary mineral from the arsenate group, occurring in the oxidation zones of copper and arsenic ores. It forms very small, acicular or bladed crystals, which most often grow together into spherical, radial aggregates, crusts, or rosettes. Individual crystals rarely exceed 1-2 mm in length, and entire aggregates typically reach several millimeters in diameter. Due to its appearance and intense color, it is valued by collectors specializing in rare minerals and micromounts. ## Physical Properties Strasimirite crystals are very brittle and soft, with a Mohs hardness of approximately 2.5. The luster is vitreous, and on fracture surfaces, it can be dull or earthy. The mineral is translucent, and in the case of very thin crystals, it can be almost transparent. Its density is higher than average, approximately 3.75 g/cm³. ## Colors and Varieties Strasimirite occurs in characteristic shades ranging from light green, through emerald green, to blue-green and pale blue. No distinct color varieties or commercial varieties are recognized. ## History and Name The mineral was discovered in 1960 in the Zapachitsa deposit in Bulgaria. It was described and named in 1968 in honor of Strashimir Dimitrov (1892–1960), a Bulgarian professor of petrography and mineralogy at the University of Sofia. The type locality is the Zapachitsa mine in the Stara Planina mountains. ## Uses Strasimirite has no industrial applications. It is solely an object of interest for collectors and a subject of scientific research.

Properties

Mohs hardness
2.5
Luster
Vitreous
Streak
Pale green
Density
3.75
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification The key diagnostic feature of strasimirite is its forms of occurrence: spherical or hemispherical aggregates with a radial internal structure, composed of fine, acicular crystals. The intense blue-green color combined with this characteristic morphology is a strong indicator. The mineral often forms thin crusts on the host rock. ## Distinguishing from Similar Minerals Strasimirite is sometimes confused with other secondary copper minerals, such as tyrolite, cornetite, pseudomalachite, or conichalcite. It is distinguished from tyrolite by the absence of pearly luster and perfect cleavage. Conichalcite and pseudomalachite typically form more massive, reniform or botryoidal aggregates with a harder structure. Final differentiation from very similar arsenates, such as geminite or eugenite, requires advanced chemical analyses (EDS) or X-ray diffraction (XRD). ## Crystal Forms Crystals are very small, elongated, acicular or bladed, flattened parallel to the {010} plane. They almost always occur as radial aggregates forming spherical or hemispherical shapes, as well as rosettes, fan-like structures, and thin coatings on rock surfaces.

Geological environment

## Genesis Strasimirite is a secondary mineral, formed in the oxidation (weathering) zones of ore deposits containing arsenic and copper. It forms as a result of oxygen-rich waters acting on primary sulfides and arsenides, such as chalcopyrite and tennantite. It forms under low-temperature conditions, in voids and fissures within rocks. ## Mineral Associations This mineral often co-occurs with other secondary copper arsenates and sulfates. The most common associated minerals include: olivenite, scorodite, cornubite, cornwallite, tyrolite, azurite, malachite, chalcanthite, as well as goethite and quartz. ## Localities The most important and well-known strasimirite localities worldwide are: - **Bulgaria** - Zapachitsa mine in the Sofia region (type locality). - **Germany** - Clara mine in the Black Forest and in the Schneeberg area in Saxony. - **Slovakia** - vicinity of Ľubietová (formerly Libethen), especially in the area of the Svätodušná mine. - **USA** - Majuba Hill mine in Pershing County, Nevada, known for excellent quality specimens. - **France** - Cap Garonne mine in the Var department.

Rarity

Rare

For collectors

## Quality Criteria The most highly prized strasimirite specimens are those with well-formed, spherical aggregates of an intense, vivid, blue-green color. The aesthetic composition is also important – specimens where delicate strasimirite spheres contrast with the rock matrix or co-occur with other well-formed secondary minerals are desirable. Due to the small size of the crystals, specimens are primarily evaluated based on the quality of the entire aggregates, their completeness, and lack of damage. ## Popular Localities The most sought-after specimens by collectors come from the Majuba Hill mine in Nevada (USA), which has yielded specimens with exceptionally aesthetic, spherical aggregates. Classic, though rarer, specimens also come from the type locality in Bulgaria and from Slovakia (Ľubietová).

Care and storage

## Cleaning Strasimirite specimens are extremely delicate and brittle. Mechanical cleaning, including the use of brushes, should be avoided. If absolutely necessary, compressed air can be carefully used from a safe distance to remove loose dust. Wet cleaning is highly inadvisable due to the risk of damaging delicate aggregates and possible reactivity with water. ## What to Avoid Contact with water, acids, detergents, and all chemicals must be strictly avoided. The mineral is sensitive to changes in temperature and humidity. It should not be heated or exposed to direct sunlight, which can cause fading or dehydration. Avoid vibrations and impacts. ## Storage It is recommended to store strasimirite specimens exclusively in specialized, sealed "micromount" boxes that protect against dust, mechanical damage, and sudden changes in humidity. Display should be away from sources of light and heat.

External references

Sources

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