Burckhardtite

Chemical formula: Pb²⁺₂(Fe³⁺Te⁶⁺)[AlSi₃O₈]O₆

Burckhardtite is a rare lead, iron, and tellurium silicate mineral, forming small, hexagonal, reddish-brown crystals.

## Characteristics Burckhardtite is a complex lead, iron, and tellurium silicate belonging to the caryopilite group. It occurs as very small, tabular or platy crystals with a hexagonal outline, reaching sizes up to 0.3 mm. It forms rosette-like aggregates or appears as single, dispersed crystals. It is a transparent mineral with a vitreous or slightly metallic luster. ## Physical Properties Due to the small size of the crystals, many physical properties have not been precisely determined. Hardness is estimated at approximately 2.5 on the Mohs scale. The density calculated from the chemical formula and unit cell parameters is 6.13 g/cm³. ## Colors and Varieties This mineral is characterized by a reddish-brown to brown color. No color varieties or commercial varieties are known. ## History and Name Burckhardtite was first described in 1978 by S.A. Williams. The mineral is named in honor of Carlos Burckhardt (1869–1935), a Swiss-Argentine geologist who made significant contributions to the geological studies of Mexico. The mineral was approved by the International Mineralogical Association (IMA) under number IMA1977-030. The type locality (locus typicus) is the Moctezuma mine in Mexico. ## Uses Burckhardtite has no industrial application. Its significance is purely scientific and as a collector's item, as a rare and interesting representative of tellurates.

Properties

Mohs hardness
2
Color
Carmine-red to violet-red, pink , brown (Mn-poor)
Luster
Vitreous to metallic
Streak
Pale red
Density
0
Cleavage
basal {001}
Fracture
Uneven
Transparency
Transparent
Crystal system
Trigonal

Diagnostic features

## Identification Identification of burckhardtite is based on its characteristic appearance – small, reddish-brown, hexagonal crystals forming rosette-like aggregates. The key is its occurrence locality (Moctezuma mine) and co-occurrence with other tellurates and tellurides. Final confirmation requires advanced analytical methods, such as chemical analysis (EDS) and X-ray diffraction (XRD). ## Distinguishing from similar minerals It can be confused with other fine-grained, red or brown secondary minerals from this locality, such as emmonsite or some iron oxides. Burckhardtite is distinguished by its hexagonal crystal form and specific chemical composition, simultaneously containing lead, iron, tellurium, aluminum, and silicon. ## Crystal forms Crystals are tabular, with a hexagonal outline. They typically form dispersed, rosette-like, or radial aggregates on the surface of the host rock.

Geological environment

## Genesis Burckhardtite is a secondary mineral, forming in the oxidation zones (gossans) of hydrothermal deposits rich in tellurium. It forms as a result of the weathering of primary tellurides and ore minerals. ## Mineral associations This mineral co-occurs with quartz, barite, as well as other rare tellurates and tellurides, such as schmitterite, emmonsite, tellurium, krennerite, sylvanite, and also with iron oxides (hematite, goethite). ## Localities The only confirmed and described occurrence of burckhardtite in the world is its type locality – La Bambolla (Moctezuma) mine, Moctezuma municipality, Sonora state, Mexico.

Rarity

Very rare

For collectors

## Quality criteria The most prized burckhardtite specimens are those with well-formed, distinct crystals forming aesthetic, rosette-like aggregates. A contrasting, light quartz matrix enhances visual appeal. Due to the microscopic size of the crystals, their sharpness and lack of damage are crucial, which is assessed under a microscope. The size of the aggregates and the richness of their occurrence on the specimen also influence its value. ## Popular localities The only source of collector specimens is the Moctezuma mine in Mexico. Material from this locality is considered classic and is the standard for this species.

Care and storage

## Cleaning Specimens should be cleaned only very carefully, using compressed air to remove dust. Due to the extreme fragility and small size of the crystals, mechanical contact (e.g., with a brush) is highly inadvisable. Contact with water may be risky. ## What to avoid All chemicals, especially acids, should be avoided. The mineral is very soft and brittle, so it should be protected from impacts, scratches, and vibrations. It should not be heated or exposed to prolonged strong light. ## Storage It is recommended to store specimens in stable, sealed "micromount" boxes that protect against dust and mechanical damage. Display should be away from sources of vibration and direct sunlight.

External references

Sources

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