Bobmeyerite

Chemical formula: Pb<sup>2+</sup><sub>4</sub>(Al<sub>3</sub>Cu<sup>2+</sup>)(Si<sub>4</sub>O<sub>12</sub>)(S<sup>6+</sup><sub>0.5</sub>Si<sub>0.5</sub>O<sub>4</sub>)(OH)<sub>7</sub>Cl·3H<sub>2</sub>O

Bobmeyerite is a very rare, blue lead and copper mineral, discovered in the Greek mines of Laurion, forming microscopic, tabular crystals.

## Characteristics Bobmeyerite is a complex hydrated chloro-sulfate-silicate of lead, aluminum, and copper. It occurs as very small, hexagonal, tabular crystals, not exceeding 0.2 mm. It forms rosette-like or radial aggregates, as well as thin crusts. Its most characteristic feature is an intense, azure-blue or sky-blue color. ## Physical properties Bobmeyerite crystals exhibit a vitreous luster. Due to the microscopic size of the crystals, many physical properties, such as hardness or density, have not been precisely measured. The density calculated based on the chemical formula and unit cell parameters is 4.23 g/cm³. ## Colors and varieties This mineral is monochromatic and has no known varieties. Its color ranges from azure-blue to sky-blue. It exhibits weak pleochroism in shades of blue. ## History and name Bobmeyerite was recognized as a new mineral by the International Mineralogical Association (IMA) in 2012 (IMA2012-060). The name honors Robert (Bob) Meyer (born 1945), a German mineral collector who specializes in minerals from Laurion and was the first to find this mineral. ## Uses Bobmeyerite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals or minerals from Laurion.

Properties

Luster
Vitreous
Streak
Light blue
Density
4.23
Cleavage
Perfect on {0001}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Trigonal

Diagnostic features

## Identification Identification of bobmeyerite is based on its characteristic azure-blue color, hexagonal, tabular crystal habit, and co-occurrence with other rare secondary minerals in the Laurion paragenesis. Due to its microscopic size, final confirmation requires advanced analytical methods, such as Raman spectroscopy or EDS analysis. ## Distinguishing from similar minerals Bobmeyerite can be confused with other blue secondary minerals from Laurion, such as chalcophyllite, which has a similar habit but crystallizes in the trigonal system. It is distinguished from chalcophyllite by the presence of aluminum and lead in its chemical composition. It may also resemble linarite, which, however, usually forms larger, prismatic crystals. ## Crystal forms Bobmeyerite forms thin, hexagonal, tabular crystals, often grouped into rosette-like or radial aggregates. It also occurs as thin coatings and crusts on the host rock.

Geological environment

## Genesis Bobmeyerite is a secondary mineral, forming in the oxidation zones of polymetallic ore deposits. Its formation is a result of the reaction of seawater with ancient lead and copper metallurgical slags left by ancient miners. ## Mineral associations This mineral co-occurs with other rare secondary minerals, such as laurionite, paralaurionite, anglesite, chalcanthite, gypsum, chalcophyllite, olivenite, azurite, and malachite. ## Localities The only confirmed occurrence of bobmeyerite in the world (type locality) is the ancient metallurgical slag heaps in the Laurion area, Attica, Greece.

Rarity

Extremely rare

For collectors

## Quality criteria The most highly valued bobmeyerite specimens are those with clearly formed, sharp crystals creating aesthetic, rosette-like aggregates. The intensity and saturation of the blue color also significantly increase the specimen's value. Contrast with the rock matrix and the presence of rare associated minerals are also important. ## Popular localities The only known locality from which all specimens originate is the historical mining region of Laurion in Greece. Specimens from this locality are the standard for this mineral.

Care and storage

## Cleaning Specimens should only be cleaned very carefully, using compressed air to remove dust. Any contact with water or chemicals is highly inadvisable due to the microscopic size and delicacy of the crystals. ## What to avoid Avoid contact with all liquids, acids, and cleaning agents. Ultrasonic cleaning is not recommended. Specimens should be protected from shocks, abrasion, and high temperatures. ## Storage It is recommended to store specimens in stable conditions, in closed, transparent "micromount" boxes, which protect them from dust, moisture, and mechanical damage.

Sources

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