Paralammerite

Chemical formula: Cu<sup>2+</sup><sub>3</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>2</sub>

Paralammerite is a rare copper arsenate, forming small, dark-green crystals, and is a dimorph of lammerite.

## Characteristics Paralammerite is a copper arsenate, most often found as small, tabular or short-prismatic crystals. It usually forms druses (crystal aggregates) and crusts on the host rock. Its crystals rarely exceed a few millimeters in length, making it primarily a micromount mineral. Its dark-green to greenish-black color is characteristic. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of about 3.5. It exhibits a vitreous luster and a high density of 4.96 g/cm³, which is noticeable even in small specimens. It is translucent, and in thicker sections, opaque. The streak is light green. ## Colors and Varieties Paralammerite occurs in a uniform range of colors, from dark, emerald green to an almost black shade of green. No color varieties or commercial varieties are distinguished. ## History and Name Paralammerite was first described in 1977 by Joseph A. Mandarino, B. D. Sturman, and M. I. Corlett. Its name refers to its close relationship with lammerite – the prefix "para-" (from Greek "beside", "near") indicates that it is a dimorph, meaning a mineral with the same chemical composition but crystallizing in a different crystallographic system. ## Uses Paralammerite has no industrial applications. Its significance is purely scientific and for collectors.

Properties

Mohs hardness
3.5
Luster
Vitreous
Streak
Light green
Density
4.96
Cleavage
Good on {010}
Fracture
Uneven
Transparency
Translucent to Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Paralammerite is identified by its characteristic dark-green color, vitreous luster, high density, and specific occurrence environment. The coexistence with other rare copper arsenates is key. Identification is most reliable for microscopic specimens, where the crystal habit can be observed. ## Distinguishing from Similar Minerals The biggest challenge is distinguishing paralammerite from lammerite, with which it is dimorphous. Definitive differentiation is only possible using advanced analytical methods, such as X-ray diffraction (XRD). It can also be confused with olivenite, which, however, usually has a different crystal habit (acicular, radial) and often a lighter, olive-green color. ## Crystal Forms Paralammerite crystals are most often tabular, flattened parallel to {010}, or short-prismatic. It forms crusts, coatings, and fine granular aggregates.

Geological environment

## Genesis Paralammerite is a secondary mineral, formed in the oxidation zones of copper and arsenic ores. It forms under low-temperature hydrothermal processes. It is also found as a sublimation product in volcanic exhalations (fumaroles). ## Mineral Associations This mineral co-occurs with other arsenates and sulfides. Its most common associations include lammerite, ludlockite, tennantite, enargite, luzonite, arsenolamprite, and native arsenic. ## Localities The most important paralammerite localities worldwide are: - El Guanaco Mine in the Antofagasta Region, Chile (type locality). - Tsumeb Mine in Namibia, known for many rare secondary minerals. - Fumaroles of the Tolbachik volcano on the Kamchatka Peninsula, Russia.

Rarity

Very rare

For collectors

## Quality Criteria The most highly prized paralammerite specimens are those with well-formed, sharp, and lustrous crystals, even if they are small. The value of a specimen is enhanced by rich coverage of the rock matrix and the presence of rare associated minerals. A contrasting color of the host rock is also a desirable feature. ## Popular Localities Specimens from the type locality (El Guanaco in Chile) and from the Tsumeb mine in Namibia are most sought after by collectors due to their historical significance and quality. Material from the Russian Tolbachik volcano is also valued, especially due to its unique formation environment.

Care and storage

## Cleaning Paralammerite specimens should be cleaned with the utmost care. The safest method is to use compressed air to remove dust or gently wipe with a dry, soft brush. Due to its arsenic content, wet methods should be avoided, as they could lead to the formation of toxic solutions. ## What to Avoid As an arsenate, paralammerite is toxic. Avoid inhaling dust and wash hands after any contact with the mineral. It is sensitive to acids and high temperatures. Due to its low hardness, it is susceptible to scratches and mechanical damage. ## Storage It is recommended to store specimens in closed, airtight containers (e.g., "membrane boxes"), away from moisture and direct sunlight. Each specimen should be clearly labeled with a warning about its toxicity.

Sources

Read more