Schultenite

Chemical formula: Pb₂+(As₅+O₃OH)

Schultenite is a rare, secondary lead arsenate, forming colorless to white, tabular crystals with an adamantine luster.

## Characteristics Schultenite is a lead arsenate that typically occurs as small, flattened or tabular crystals. It often forms rosette-like or fan-shaped aggregates, as well as coatings and efflorescences. Individual crystals are usually colorless, white, or grayish, exhibiting high transparency and a strong, almost adamantine luster, which gives them a distinctive appearance. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of about 2.5, meaning it can be scratched with a fingernail. It is also very dense due to its high lead content. The crystals are brittle and easily damaged. Luster is one of its most prominent features – described as resinous to adamantine. ## Colors and Varieties Schultenite is most often colorless or white. It can take on shades of gray, and occasionally yellowish or greenish coloration, likely caused by the presence of impurities. There are no named varieties of this mineral. ## History and Name The mineral was first described in 1926 by L.J. Spencer. Its name commemorates Baron August Benjamin de Schulten (1856-1912), a Finnish chemist and mineralogist from the University of Helsinki, who was renowned for synthesizing minerals for research purposes, including an artificial equivalent of schultenite, even before its discovery in nature. ## Uses Due to its rarity and small crystal size, schultenite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals or minerals from specific localities.

Properties

Mohs hardness: 2.5
Luster: Adamantine
Streak: White
Density: 5.94
Cleavage: Perfect on {100}
Fracture: Conchoidal
Transparency: Transparent to translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Schultenite can be identified by its characteristic, very strong resinous or adamantine luster, high density (the specimen is surprisingly heavy for its size), and crystal habit – usually small, tabular, often gathered in rosette-like aggregates. It is very soft (hardness approx. 2.5). ## Distinguishing from Similar Minerals Schultenite is sometimes confused with other colorless or white secondary minerals of the oxidation zone, such as cerussite, anglesite, or mimetite. It is distinguished from cerussite and anglesite by its lower hardness and specific, adamantine luster. Unlike mimetite, schultenite rarely forms hexagonal crystals, and its crystals are usually flattened and tabular.

Geological environment

## Genesis Schultenite is a rare secondary mineral, forming in the oxidation (weathering) zones of polymetallic ore deposits rich in lead and arsenic. It forms as a result of the oxidation of arsenopyrite and galena in the presence of water. ## Mineral Associations This mineral often occurs in association with other secondary lead and arsenic minerals. The most common associations include: mimetite, pharmacosiderite, beudantite, segnitite, carminite, scorodite, anglesite, and cerussite. ## Localities The type locality, from which this mineral was first described, is the Tsumeb mine in Namibia, known for exceptional schultenite specimens. Other significant localities worldwide include the San Rafael mine in Nevada (USA), the Clara mine in the Black Forest (Germany), and the Lavrion area in Greece.

Rarity

Rare

For collectors

## Quality Criteria The most prized specimens by collectors are those with well-formed, sharp, and transparent crystals with a strong luster. Aesthetic aggregates, such as rosettes or fans, set on a contrasting rock matrix, are also highly valued. Crystal size is a key factor – specimens with crystals exceeding several millimeters are considered exceptional. Clarity (lack of inclusions) and absence of damage significantly increase the specimen's value. ## Popular Localities By far the most sought-after and classic schultenite specimens come from the Tsumeb mine in Namibia. Specimens from this locality, often in the form of beautiful, colorless rosettes, are considered the global standard for this mineral.

Care and storage

## Cleaning Schultenite specimens should be cleaned with the utmost care. The safest method is to use compressed air to remove dust. If wet cleaning is necessary, use only distilled water and a very soft brush, avoiding vigorous rubbing. After cleaning, the specimen should be thoroughly dried immediately. ## What to Avoid Schultenite is a brittle and soft mineral, susceptible to mechanical damage. Avoid contact with acids and other chemicals that may damage it. It should not be cleaned ultrasonically. As a lead arsenate, it is toxic – avoid inhaling dust and wash hands after any contact with the mineral. ## Storage Schultenite specimens are best stored in separate, padded display boxes to protect them from scratches and impacts. They should be kept away from moisture and heat sources. Due to its toxicity, it should be stored out of reach of children and pets.

Sources

IMA Mineral List (CNMNC)