Zincgartrellite

Chemical formula: Pb<sup>2+</sup>Zn<sup>2+</sup><sub>2</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O,OH)<sub>2</sub>

Zincgartrellite is a rare lead zinc arsenate, forming microscopic, yellowish-green spherulitic aggregates.

## Characteristics Zincgartrellite is a hydrated lead zinc arsenate belonging to the tsumcorite group. It occurs as very small, spherulitic or radial aggregates, rarely exceeding 0.5 mm in diameter. Individual crystals forming these aggregates are bladed or acicular and are too small to be seen with the naked eye. Due to its size, it is a mineral primarily accessible to advanced micromount collectors. ## Physical Properties Zincgartrellite crystals exhibit a vitreous to slightly adamantine luster. Hardness on the Mohs scale is estimated at approximately 4.5. It is a relatively dense mineral, which is due to the presence of lead in its chemical composition. ## Colors and Varieties The mineral is characterized by colors ranging from pale yellow, through yellowish-green, to green. No varieties have been distinguished. ## History and Name Zincgartrellite was first described in 1998 by Werner Krause, Klaus Belendorff, Heinz-Jürgen Bernhardt, and Catherine McCammon. Its name refers to its chemical composition – it is the zinc analog of gartrellite, in which zinc replaces copper. The name gartrellite honors the Australian mineral collector, Benjamin Gartrell.

Properties

Mohs hardness
4.5
Luster
Vitreous to Adamantine
Streak
Pale yellow
Density
5.45
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Translucent
Crystal system
Triclinic

Diagnostic features

## Identification Identification of zincgartrellite is possible almost exclusively based on chemical (EDS) and crystallographic (XRD) analysis due to its microscopic size and occurrence in complex parageneses. Visually, under high magnification, characteristic features are small, yellowish-green spherulitic aggregates. ## Distinguishing from Similar Minerals It can be confused with other minerals from the tsumcorite group, such as gartrellite (usually greener, contains copper), tsumcorite (different composition), or helmutwinklerite. Differentiation without advanced analysis is practically impossible. Other secondary arsenate minerals, such as mimetite or adamite, may also have a similar appearance. ## Crystal Forms Zincgartrellite forms spherulitic or radial aggregates composed of microscopic, elongated crystals with a bladed or acicular habit.

Geological environment

## Genesis It is a secondary mineral, forming in the oxidation zones (gossans) of polymetallic ore deposits rich in lead, zinc, and arsenic. It forms as a result of the weathering of primary sulfides, mainly galena, sphalerite, and arsenopyrite. ## Mineral Associations It often co-occurs with other rare secondary minerals. Its typical associated minerals include: anglesite, cerussite, beudantite, segnitite, mimetite, wulfenite, stolzite, as well as other minerals from the tsumcorite group like gartrellite and helmutwinklerite. ## Localities The most important localities worldwide, from which the best-formed specimens originate, are: - Tsumeb Mine in Namibia (type locality). - Broken Hill in New South Wales, Australia. - Gara-Djebilet in Tindouf Province, Algeria. - Preguiça Mine in Sobral da Adiça, Portugal.

Rarity

Very rare

For collectors

## Quality Criteria The quality of zincgartrellite specimens is primarily assessed based on the richness and aesthetics of the aggregates on the rock matrix. The most prized specimens are those with numerous, well-formed spherulites of intense, yellowish-green color, contrasting with the substrate. The absence of damage and the presence of rare associated minerals, which enhance the scientific and visual value of the specimen, are also important. ## Popular Localities The most sought-after specimens by collectors come from the Tsumeb mine in Namibia, which is known for providing the world's best examples of this mineral.

Care and storage

## Cleaning Specimens should only be cleaned with compressed air to remove dust. Due to the microscopic size and fragility of the crystals, any other method, including the use of water or brushes, risks irreversible damage to the aggregates. ## What to Avoid Avoid contact with water, chemicals (especially acids), and ultrasound. The mineral is brittle and sensitive to mechanical shocks. As an arsenate, it is toxic – avoid inhaling dust and wash hands after any contact. ## Storage It is recommended to store specimens exclusively in specialized "micromount" boxes, protecting them from dust, moisture, and mechanical damage. Display should be away from sources of vibration.

Sources

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