Tlapallite
Chemical formula: (Ca,Pb<sup>2+</sup>)<sub>3</sub>CaCu<sup>2+</sup><sub>6</sub>[Te<sup>4+</sup><sub>3</sub>Te<sup>6+</sup>O<sub>12</sub>]<sub>2</sub>(Te<sup>4+</sup>O<sub>3</sub>)<sub>2</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>·3H<sub>2</sub>O
Tlapallite is a very rare copper, calcium, and lead tellurate, forming microscopic, green coatings and aggregates.
Properties
- Mohs hardness
- 3
- Luster
- Earthy
- Streak
- Light green
- Cleavage
- Perfect on {0001}
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Hexagonal
Diagnostic features
## Identification Identification of tlapallite is based on its characteristic emerald-green color, earthy or spherical aggregates, and occurrence in association with other rare tellurates and tellurides. Identification is practically only possible under laboratory conditions using advanced analytical methods (e.g., EDS/WDS, XRD) due to the microscopic size of the crystals. ## Distinguishing from Similar Minerals Tlapallite can be confused with other secondary green copper minerals, such as malachite, brochantite, or other rare tellurates (e.g., quetzalcoatlite, xocomecatlite). Visual distinction is impossible. Tlapallite is distinguished by its unique chemical composition, containing tellurium in two oxidation states (Te⁴⁺ and Te⁶⁺), sulfate, copper, lead, and calcium simultaneously. ## Crystal Forms The mineral forms microscopic, hexagonal plates that combine into spherical or rosette-like aggregates. It often occurs as earthy, powdery coatings and thin crusts on the surface of the host rock.
Geological environment
## Genesis Tlapallite is a secondary mineral, formed in the oxidation (weathering) zone of hydrothermal deposits rich in tellurium, copper, and lead. It forms under low-temperature conditions as a result of the alteration of primary tellurides. ## Mineral Associations This mineral co-occurs with other, often equally rare, minerals of the oxidation zone. The most common associations include: native tellurium, quartz, baryte, as well as tellurates and tellurides such as quetzalcoatlite, xocomecatlite, eztlite, carlfriesite, emmonsite, and teineite. ## Localities The most important and historical locality for tlapallite is its type locality – the La Moctezuma mine (also known as Bambolla) in Sonora, Mexico. It has also been identified in the Emerald mine in the Tombstone district, Arizona (USA), and in the Kawazu mine in Shizuoka Prefecture, Japan.
Rarity
Very rare
For collectors
## Quality Criteria For tlapallite, as a "micromount" type mineral, the most important criterion is the richness and aesthetics of the microscopic aggregates on the rock matrix. Specimens with clearly formed, spherical or rosette-like clusters of intense, emerald-green color are most highly valued. Association with other rare minerals is also important, as it increases the scientific and collectible value of the specimen. ## Popular Localities Specimens from the type locality – the La Moctezuma mine in Mexico – are by far the most valued and sought after by collectors. Material from the Emerald mine in Arizona is also known, but Mexican specimens are considered classic for this species.
Care and storage
## Cleaning Tlapallite specimens should not be cleaned mechanically or chemically. Any attempts at cleaning can irreversibly damage the delicate, microscopic aggregates. If dust removal is necessary, it can be done very carefully with a soft brush or a photographic air blower, avoiding direct contact with the mineral. ## What to Avoid Avoid contact with water, acids, solvents, and all chemical agents. The mineral is very soft and susceptible to abrasion. Protect it from vibrations, shocks, and temperature changes. ## Storage Tlapallite specimens should be stored exclusively in sealed, closable "micromount" boxes to protect them from dust, mechanical damage, and moisture. They should not be exposed to direct sunlight.