Gartrellite

Chemical formula: Pb₂+Cu₂+Fe₃+(As₅+O₄)₂(OH)·H₂O

Gartrellite is a rare secondary mineral of the tsumcorite group, forming microscopic, yellowish-green crystals and coatings in the oxidation zones of ore deposits.

## Characteristics Gartrellite is a hydrated lead, copper, and iron arsenate, belonging to the tsumcorite group. It most often occurs as very fine, radial or spherulitic aggregates, as well as earthy coatings and crusts on other minerals. Individual crystals are extremely small, usually less than 0.1 mm in size, and have a tabular or bladed habit. Due to its microscopic size, it is a mineral primarily valued by specialized collectors (micromounters). ## Physical Properties Gartrellite crystals exhibit a vitreous or slightly adamantine luster. The mineral is translucent. Its Mohs hardness is approximately 4.5, and its density is high, typical for lead-bearing minerals, at about 5.25 g/cm³. ## Colors and Varieties This mineral is characterized by vivid colors, ranging from yellow, through yellowish-green, to green. No commercial or color varieties are distinguished. ## History and Name The name gartrellite comes from Ben Gartrell (b. 1951), an Australian chemist and mineral collector, who first discovered this mineral in the Ashburton Downs mine in Western Australia. The mineral was described and approved by the International Mineralogical Association (IMA) in 1989. It is a product of the weathering of primary minerals such as galena, chalcopyrite, and arsenopyrite. ## Uses Due to its rarity and microscopic size, gartrellite has no industrial application. It is of scientific and collector's interest only.

Properties

Mohs hardness: 4.5
Luster: Vitreous to Adamantine
Streak: Pale yellow
Density: 5.25
Cleavage: Perfect on {001}
Fracture: Uneven
Transparency: Translucent
Crystal system: Triclinic

Diagnostic features

## Identification Amateur identification of gartrellite is practically impossible due to the microscopic size of its crystals. Recognition relies on its characteristic yellowish-green color, radial aggregates, and co-occurrence with other arsenates in oxidation zones. Definitive identification requires advanced analytical methods, such as EDS spectroscopy or X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with many other secondary arsenates of similar colors, such as agardite, olivenite, mimetite, or other minerals from the tsumcorite group (e.g., tsumcorite, helmutwinklerite). Differentiation without specialized equipment is impossible. Gartrellite is distinguished by its unique chemical composition, simultaneously containing lead, copper, and iron. ## Crystal Forms Gartrellite forms very small, tabular or bladed crystals, most often occurring as radial, spherical, or spherulitic aggregates. It is also found as earthy coatings and crusts.

Geological environment

## Genesis Gartrellite is a secondary mineral, forming in the oxidation zones (gossans) of polymetallic ore deposits. It forms as a result of weathering and alteration of primary minerals containing lead, copper, iron, and arsenic, such as galena, chalcopyrite, and arsenopyrite, under low temperature and pressure conditions. ## Mineral Associations This mineral often co-occurs with other secondary arsenates and sulfates. The most common associated minerals include: beudantite, segnitite, duftite, bayldonite, mimetite, olivenite, anglesite, cerussite, goethite, and quartz. ## Localities The most important and well-known gartrellite localities worldwide include: Tsumeb mine in Namibia, which yields some of the best specimens; Ashburton Downs in Western Australia (type locality); Clara mine in the Black Forest, Germany; Lavrion in Greece; and several localities in Cornwall, United Kingdom.

Rarity

Very rare

For collectors

## Quality Criteria For gartrellite collectors, the most important criteria are: crystal size and habit (though always microscopic), intensity and purity of color (vivid, yellowish-green hues are preferred), and the richness and aesthetics of aggregates on the rock matrix. Specimens where gartrellite forms well-defined, radial rosettes or spherical clusters are highly valued. Association with other rare secondary minerals is also important. ## Popular Localities The most sought-after gartrellite specimens by collectors come from the Tsumeb mine in Namibia, renowned for its exceptional quality and diversity of secondary minerals. Specimens from the German Clara mine and Greek Lavrion, where gartrellite forms aesthetic compositions with other arsenates, are also highly prized.

Care and storage

## Cleaning Gartrellite specimens should be cleaned very carefully, preferably using compressed air to remove dust. Due to the microscopic size of the crystals and their fragility, mechanical contact, including brushing, should be avoided. If liquid is necessary, only distilled water or isopropyl alcohol in an ultrasonic cleaner should be used with great caution. ## What to Avoid Contact with acids and other aggressive chemicals that can damage the mineral should be avoided. Gartrellite is a secondary mineral and can be sensitive to changes in humidity and temperature. It should not be heated or exposed to prolonged strong light. ## Storage Gartrellite specimens, especially microscopic ones (micromounts), should be stored in specialized, sealed boxes that protect them from dust, mechanical damage, and sudden environmental changes. A label with precise locality information is crucial for the specimen's value.

Sources

IMA Mineral List (CNMNC)