Pararsenolamprite

Chemical formula: As

Pararsenolamprite is a rare, orthorhombic polymorphic form of arsenic, forming lamellae with a metallic luster that quickly darken in air.

## Characteristics Pararsenolamprite is one of the natural, crystalline forms of arsenic (As), belonging to the native elements. It is an orthorhombic polymorph of arsenic, meaning it has the same chemical composition as native arsenic (trigonal) and arsenolamprite (another orthorhombic variety), but differs from them in its internal structure. It forms characteristic, platy or scaly aggregates, often with a radial or spherulitic structure. On a fresh surface, it has a tin-white color and a strong, metallic luster. Its special feature is rapid oxidation in air, as a result of which it becomes covered with a dark gray or black tarnish. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of about 2. It is brittle and has excellent, unidirectional cleavage, which accounts for its platy appearance. The density is about 5.88 g/cm³, making it a heavy mineral. It is completely opaque. ## Colors and Varieties Pararsenolamprite does not form color varieties. Its only characteristic color is tin-white on a fresh fracture. However, this color is unstable and quickly turns dark gray or black due to contact with oxygen from the air. ## History and Name The mineral's name refers to its close relationship with arsenolamprite and comes from the Greek word *para* (παρά), meaning "beside" or "near". It was described as a distinct mineral in 1957 by Paul Ramdohr. The Palmbaum mine in Gehringswalde, in the Marienberg area of Saxony (Germany), was designated as the type locality (locus typicus). ## Uses Due to its rarity and toxicity, pararsenolamprite has no industrial application. It is of scientific and collector's interest only, being sought after by specialists collecting systematic minerals or native elements.

Properties

Mohs hardness
2
Luster
Metallic
Streak
Black
Density
5.88
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Opaque
Crystal system
Orthorhombic

Diagnostic features

## Identification Key diagnostic features of pararsenolamprite are its tin-white color on a fresh surface, strong metallic luster, excellent cleavage leading to the formation of platy or scaly aggregates, and rapid darkening in air. Its high density is also helpful in identification. ## Distinguishing from Similar Minerals - **Native arsenic:** Crystallizes in the trigonal system and more often forms botryoidal, reniform, or granular aggregates. It less frequently exhibits such excellent cleavage. - **Arsenolamprite:** Is another orthorhombic polymorph of arsenic. Visual differentiation of these two minerals is impossible and requires specialized studies, such as X-ray diffraction (XRD). - **Native antimony and stibarsen:** Are visually very similar. Certain differentiation requires chemical analysis to determine the presence or absence of antimony. - **Graphite:** Is significantly lighter, softer (hardness 1-2), has a greasy feel, and leaves a dark streak on paper. - **Molybdenite:** Is flexible (elastic), whereas pararsenolamprite is brittle. Molybdenite's streak is grayish-green. ## Crystal Forms Well-formed crystals are extremely rare. Pararsenolamprite occurs almost exclusively in the form of aggregates composed of thin lamellae or scales, which often arrange into radial, fan-shaped, or spherulitic structures.

Geological environment

## Genesis Pararsenolamprite is a mineral of hydrothermal origin. It forms at relatively low temperatures in ore veins rich in arsenic, often in paragenesis with other arsenic minerals. ## Mineral Associations It most commonly co-occurs with native arsenic, arsenolamprite, realgar, orpiment, as well as löllingite, native bismuth, galena, and sphalerite. ## Localities Among the most important and classic localities for pararsenolamprite are: - **Germany:** Palmbaum mine in Marienberg and the St. Andreasberg area in the Harz mountains. - **Czech Republic:** Jáchymov (St. Joachimsthal). - **Japan:** Akatani mine in Fukui Prefecture, known for well-formed, radial aggregates. - **USA:** Franklin and Sterling Hill deposits in New Jersey.

Rarity

Rare

For collectors

## Quality Criteria The collector's value of pararsenolamprite depends on its form of occurrence. Specimens with well-formed, radial or spherulitic aggregates with a distinct structure are most highly prized. Large, undamaged lamellae are also desirable. Contrast with the surrounding matrix and the presence of rare associated minerals enhance the attractiveness of the specimen. Although a fresh, metallic luster is desirable, the characteristic dark patina is accepted as a natural feature of the mineral. ## Popular Localities The historical localities in Germany (Marienberg, St. Andreasberg) are considered classic, providing the best specimens. Radial aggregates from the Akatani mine in Japan are also highly valued in the collector's market.

Care and storage

## Cleaning Pararsenolamprite specimens should only be dry-cleaned, using a soft brush to remove dust. Avoid any contact with water and other liquids, which can accelerate the oxidation process and damage the specimen. ## What to Avoid **Warning: The mineral is toxic.** It contains arsenic. Avoid inhaling dust and wash hands after any contact with the specimen. Pararsenolamprite is sensitive to moisture and oxygen from the air, which cause it to darken. It should not be exposed to chemicals, especially acids. ## Storage It is recommended to store specimens in airtight, sealed containers (e.g., "perky box" type) to limit air and moisture access. It is best to keep it in a dry and dark place. Each specimen should be clearly labeled with information about its toxicity.

Sources

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