Flaggite

Chemical formula: Pb<sup>2+</sup><sub>4</sub>Cu<sup>2+</sup><sub>4</sub>Te<sup>6+</sup><sub>2</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>O<sub>11</sub>(OH)<sub>2</sub>(H<sub>2</sub>O)

Flaggite is an extremely rare secondary mineral, a hydrated lead and copper tellurate-sulfate, forming microscopic, dark-green flakes.

## Characteristics Flaggite is a mineral from the sulfate and tellurate group, occurring as microscopic aggregates. Typical specimens consist of very small, thin, platy or bladed crystals, which often arrange into rosette-like or fan-like forms. Its color is dark green, sometimes transitioning to greenish-black. Due to the size of its crystals, it is a typical micromount mineral, impossible to observe with the naked eye in the form of well-developed crystals. ## Physical Properties Flaggite crystals exhibit a submetallic luster, in places greasy. In thin fragments, the mineral is translucent, while in thicker aggregates it becomes opaque. It is characterized by perfect cleavage in one plane, which accounts for its platy structure. The Mohs hardness is approximately 3. The density calculated based on the chemical formula and unit cell parameters is about 6.5 g/cm³, which is a high value, typical for lead-bearing minerals. ## Colors and Varieties This mineral occurs exclusively in shades of dark green. No color varieties or commercial varieties are known. ## History and Name Flaggite was officially recognized as a new mineral species by the International Mineralogical Association (IMA) in 2020. Its name honors Arthur Leonard Flagg (1883–1961), an American mining engineer, mineralogist, and renowned mineral collector from Arizona. The discovery was made on material originating from the historic Tombstone mining district in Arizona, USA. ## Uses As an extremely rare mineral occurring only in microscopic specimens, flaggite has no industrial application. It is solely an object of scientific interest and a prized acquisition for specialized collectors of micromount minerals.

Properties

Mohs hardness
3
Luster
Sub-metallic to Greasy
Streak
Light green
Density
6.5
Cleavage
Perfect on {001}
Transparency
Translucent in thin fragments, Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Amateur identification of flaggite is practically impossible. Key features include its dark green color, platy crystal habit, high density, and specific occurrence. Definitive identification requires advanced analytical techniques, such as X-ray diffraction (XRD) and chemical microanalysis (EDS). ## Differentiation from Similar Minerals Flaggite can be confused with other rare, green, secondary copper and lead minerals from the type locality, such as backite or oboyerite. Visual differentiation of these minerals is unfeasible and relies solely on laboratory analysis. ## Crystal Forms Flaggite forms thin, tabular or bladed crystals with a rectangular or hexagonal cross-section. These crystals usually occur as small, radial or subparallel aggregates.

Geological environment

## Genesis Flaggite is a secondary mineral, formed in the oxidation zone of polymetallic hydrothermal deposits. It crystallizes as a result of weathering of primary ores containing tellurium, lead, copper, and sulfides under low temperature and pressure conditions. ## Mineral Associations This mineral co-occurs with a whole range of other rare, secondary minerals, especially tellurates and sulfates. The most common associated minerals in the type locality include: backite, utahite, jensenite, leisingite, cerussite, anglesite, and quartz. ## Localities The only confirmed occurrence of flaggite in the world is its type locality – the Grand Central mine and adjacent historic workings (e.g., Toughnut Mine) in the Tombstone district, Cochise County, Arizona, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of collectible flaggite specimens, being a micromount mineral, is assessed based on different criteria than for macroscopic specimens. Highly valued are rich aggregates of well-formed, sharp crystals, forming aesthetic clusters. The presence of rare associated minerals on the same piece of matrix rock is also of great importance. ## Popular Localities The only source of flaggite specimens is the Tombstone mining district in Arizona. Specimens from this locality are considered classic and most sought after by collectors specializing in rare minerals and micromounts.

Care and storage

## Cleaning Flaggite specimens are extremely delicate and small. To remove dust, use only a soft brush or a stream of compressed air from a safe distance. Avoid any contact with water and other liquids. ## What to Avoid The mineral is sensitive to chemicals, especially acids. Ultrasonic cleaners and steam cleaning should not be used. It should be protected from mechanical damage, scratching, and sudden temperature changes. ## Storage Flaggite specimens should be stored in specialized micromount boxes, which protect them from dust, moisture, and physical damage. Storage in stable room conditions, away from direct sunlight, is recommended.

Sources

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