Lemanskiite

Chemical formula: NaCaCu²⁺₅(As⁵⁺O₄)₄Cl(H₂O)₃

Lemanskiite is a very rare copper mineral, forming characteristic blue-green, acicular crystals aggregated into spherical forms.

## Characteristics Lemanskiite is a hydrated sodium, calcium, and copper arsenate with additional chlorine. It occurs as fine, acicular or hair-like crystals, which most often form radial or spherical aggregates and clusters. Individual crystals are elongated and very slender. Due to its composition and the presence of copper, this mineral has an intense, blue-green color. ## Physical Properties Lemanskiite crystals exhibit a vitreous luster. They are transparent to translucent. The Mohs hardness is about 2, making it a very soft and delicate mineral. It is relatively heavy for its appearance, with a density of 3.75 g/cm³. ## Colors and Varieties This mineral is known exclusively in one characteristic color – a vivid, blue-green. No color or commercial varieties are distinguished. ## History and Name Lemanskiite was discovered in the "El Guanaco" mine in the Antofagasta region of Chile. It was described in 2001 by Jochen Schlüter, Karl-Heinz Klaska, and G. Gebhard. The mineral is named in honor of Chester "Chet" Lemanski (born 1947), an American mineral collector who specialized in systematics and provided many rare specimens for scientific research. ## Uses Lemanskiite has no industrial application. Its significance is purely scientific and as a collector's item, being a coveted object for specialized collectors of rare minerals.

Properties

Mohs hardness: 2-3
Color: Sky blue
Luster: Vitreous
Streak: Sky blue
Density: 3.78
Cleavage: (001)
Fracture: Irregular/Uneven
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Lemanskiite can be identified by its characteristic mode of occurrence – spherical or radial aggregates composed of very fine, acicular crystals of an intense blue-green color. The place of origin (El Guanaco mine) and co-occurrence with other rare copper arsenates are also key. ## Differentiation from Similar Minerals It can be confused with other secondary, acicular copper minerals, such as chalcanthite, brochantite, or some zeolites. However, lemanskiite is distinguished by its unique form of spherical aggregates, specific hue, extreme rarity, and occurrence in only one locality. Water solubility is also a diagnostic feature, differentiating it from most similar minerals. ## Crystal Forms Crystals are acicular, very elongated along the [001] axis. They usually form radial, spherical, or hemispherical aggregates up to 1 mm in diameter, growing on the host rock.

Geological environment

## Genesis Lemanskiite is a secondary mineral, forming in the oxidation zones (gossans) of polymetallic deposits rich in copper and arsenic. It forms under very dry, desert climatic conditions as a result of the weathering processes of primary sulfide ores, such as enargite. ## Mineral Associations This mineral co-occurs with other rare arsenates and sulfates. It is most often found in association with minerals such as: guanacoite, arsenogoyazite, eulytite, anglesite, gypsum, quartz, and iron oxides (hematite, goethite). ## Localities The only confirmed locality of lemanskiite in the world is its type locality – the "El Guanaco" mine, located near Santa Catalina, in the Antofagasta province of northern Chile.

Rarity

Extremely rare

For collectors

## Quality Criteria The most prized lemanskiite specimens are those with well-formed, undamaged spherical aggregates of intense, vivid color, contrasting with the light host rock. The size of the aggregates (though always small, usually up to 1 mm) and their quantity on the specimen also affect the value. The purity of the specimen and the absence of mechanical damage are crucial due to the extreme delicacy of the mineral. ## Popular Localities Since lemanskiite occurs in only one place in the world – the El Guanaco mine in Chile – all collector specimens come from this exact locality. This is a classic example of a mineral from a single, type locality.

Care and storage

## Cleaning Lemanskiite specimens are extremely delicate and fragile. Mechanical or chemical cleaning is not recommended. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust particles. Contact with water should be avoided, as the mineral is soluble in it. ## What to Avoid - **Water and moisture:** Lemanskiite is soluble in water and acids. It should be protected from humid air. - **Shocks and touch:** Acicular crystals are extremely fragile and easily damaged. - **High temperature:** This can cause the loss of water from its structure and a change in properties. - **Chemicals:** Avoid all cleaning agents and solvents. ## Storage It is recommended to store specimens exclusively in closed, padded "micromount" boxes or in display cases with controlled humidity. Avoid exposure to open air and places where it might be subjected to vibrations or accidental touching.