Parnauite

Chemical formula: Cu²⁺₉(As⁵⁺O₄)₂(S⁶⁺O₄)(OH)₁₀(H₂O)₄·₃H₂O

Parnauite is a rare, secondary copper and arsenic mineral, forming characteristic rosette-like aggregates of tiny, emerald-green crystals.

## Characteristics Parnauite is a hydrated basic copper sulfate and arsenate. It occurs as very small, bladed or acicular crystals, which almost always form spherical or hemispherical aggregates with a radial internal structure. Individual crystals are rarely visible to the naked eye, and the clusters resemble small rosettes, fans, or sea urchins, typically reaching sizes up to several millimeters. ## Physical Properties Parnauite crystals are very brittle and delicate. This mineral is characterized by a vitreous luster. Due to the small size of the crystals, many physical properties, such as density or hardness, are difficult to measure precisely. ## Colors and Varieties Parnauite has a characteristic, vivid color, ranging from emerald-green to bluish-green. No color or commercial varieties are distinguished. ## History and Name The mineral was named in honor of Clarence

Properties

Mohs hardness: 2
Color: Pale blue, green, dark green, blue-green, yellow-green
Luster: Vitreous
Streak: Light green
Density: 3.09
Cleavage: Perfect on {100}
Fracture: Uneven
Transparency: Translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification A characteristic feature of parnauite is its vivid green, spherical aggregates with a radial structure, resembling small sea urchins or rosettes. Its occurrence in the oxidation zones of copper and arsenic deposits facilitates identification. ## Distinguishing from Similar Minerals It can be confused with other secondary copper minerals of similar color and aggregate form, such as tyrolite, brochantite, or some forms of malachite. Final differentiation often requires chemical (EDS) or X-ray (XRD) analysis, due to the presence of both sulfates and arsenates in its structure. Compared to tyrolite, parnauite forms more three-dimensional, spherical aggregates, rather than flat fans. ## Crystal Forms Parnauite forms small, elongated, bladed crystals, which almost always occur as radial, spherical, or hemispherical aggregates. Fan-shaped or acicular clusters are observed less frequently.

Geological environment

## Genesis Parnauite is a secondary mineral, formed in the oxidation (weathering) zones of polymetallic ore deposits rich in copper and arsenic. It forms as a result of the reaction of acidic, sulfate-rich waters with primary minerals containing copper and arsenic, such as chalcopyrite and arsenopyrite, or through the alteration of other secondary minerals. ## Mineral Associations It often co-occurs with other secondary minerals of the oxidation zone, such as azurite, brochantite, chalcophyllite, cyanotrichite, olivenite, tyrolite, tenorite, as well as gypsum and quartz. ## Localities The most important localities from which well-formed specimens originate are the Majuba Hill mine in Pershing County (Nevada, USA) - the type locality, as well as the Clara mine in the Black Forest (Germany), Cap Garonne (France), and the Tintic District in Utah (USA). It also occurs in many other localities worldwide, but usually in much smaller quantities.

Rarity

Very rare

For collectors

## Quality Criteria The most valued by collectors are specimens with well-formed, spherical aggregates of intense, emerald-green color, contrasting with the color of the host rock. Rich crystal groups covering a larger matrix surface are also highly rated. Due to the small size of the clusters, parnauite is primarily of interest to collectors specializing in microminerals (micromounts). ## Popular Localities Specimens from the Majuba Hill mine in Nevada (USA) and the Clara mine in Germany are considered the best in the world. They provide exemplary, spherical aggregates with vivid color.

Care and storage

## Cleaning Parnauite specimens should only be cleaned very carefully, using compressed air to remove dust. Due to extreme brittleness and solubility in acids, contact with water and all chemicals should be avoided. ## What to Avoid Contact with water, acids, and other cleaning agents must be strictly avoided. The mineral is very sensitive to shocks and vibrations, which can cause delicate aggregates to disintegrate. It should not be heated or exposed to ultrasound. ## Storage It is recommended to store specimens in closed, padded boxes (micromount type) to protect them from dust, moisture, and mechanical damage. Display should be in stable conditions, away from sources of vibration.