Paulhlavaite

Chemical formula: CaCu<sup>2+</sup>Te<sup>4+</sup><sub>4</sub>O<sub>10</sub>

Paulhlavaite is an extremely rare calcium copper tellurite, forming microscopic, tabular crystals of an intense green color.

## Characteristics Paulhlavaite is an oxide mineral, specifically a calcium copper tellurite. It occurs as extremely small, tabular or bladed crystals, reaching up to 0.2 mm in size. These crystals are transparent and characterized by a vivid, emerald-green color and a vitreous luster. Due to its microscopic size, it is a mineral accessible only to specialized micromounters. ## Physical Properties Paulhlavaite crystals are too small to precisely determine their hardness or density, but based on their chemical composition, it can be assumed to be a relatively dense mineral. It exhibits perfect cleavage in one direction, which is visible on larger crystal fragments. It is transparent and has a pale green streak. ## Colors and Varieties This mineral occurs exclusively in one color – emerald-green. No color varieties or commercial names are known. ## History and Name Paulhlavaite was discovered at the historic gold and tellurium deposit in Otto Mountain, near Baker in San Bernardino County, California, USA. It was officially recognized as a new mineral by the International Mineralogical Association (IMA) in 2011 (IMA2011-031). The name honors Pavel Hlava (1963–2003), an American mineralogist and microprobe analyst at Sandia National Laboratories, who first identified this mineral phase but passed away before completing its description.

Properties

Luster
Vitreous
Streak
Light green
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of paulhlavaite is possible only using advanced analytical techniques, such as energy-dispersive spectroscopy (EDS/EDX) in conjunction with electron microscopy, due to its microscopic size. Visual characteristics under high magnification include the distinctive emerald-green color, tabular crystal habit, and vitreous luster. ## Distinguishing from Similar Minerals Paulhlavaite can be confused with other secondary, green tellurium minerals, such as mackayite or poughite, which may co-occur in the same environment. Differentiation relies on chemical composition analysis – the presence of calcium and copper in specific proportions is key. Visually, it is practically indistinguishable without specialized equipment. ## Crystal Forms It forms very small, thin, tabular crystals with a bladed habit, often grouped into small aggregates or dispersed on the surface of the host rock.

Geological environment

## Genesis Paulhlavaite is a secondary mineral, formed in the oxidation (weathering) zone of hydrothermal gold and tellurium deposits. It forms as a result of the alteration of primary tellurides under low temperature and pressure conditions, in the presence of solutions rich in copper and calcium. ## Mineral Associations This mineral co-occurs with other, often equally rare, secondary tellurium minerals. At the type locality (Otto Mountain), it has been found in association with mackayite, poughite, tellurite, quartz, barite, as well as native gold and tellurium. ## Localities The only confirmed occurrence of paulhlavaite in the world is its type locality: the Otto Mountain deposit, located approximately 11 km southeast of the town of Baker, in San Bernardino County, California, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria Due to its extreme rarity and microscopic size, every analytically confirmed paulhlavaite specimen is extremely valuable. The most highly prized specimens are those where the crystals, though small, are well-formed, have an intense green color, and are grouped into aggregates visible under a microscope. Contrast with the surrounding host rock (matrix) and the presence of other rare associated minerals are also important. ## Popular Localities The only source of specimens is the historic Otto Mountain deposit in California. Material from this locality is highly sought after by specialized micromounters.

Care and storage

## Cleaning Paulhlavaite specimens, due to their microscopic size and extreme rarity, practically never require cleaning. Any attempts at mechanical or chemical cleaning risk irreversible damage or loss of the mineral. If dust removal is absolutely necessary, a gentle stream of compressed air from a distance can be used. ## What to Avoid Avoid contact with any chemicals, including acids and bases. The mineral is likely sensitive to changes in temperature and humidity. It should not be exposed to direct sunlight, which may cause it to fade. Avoid vibrations and shocks. ## Storage Specimens should be stored exclusively in specialized, sealed "micromount" boxes, which protect them from dust, mechanical damage, and loss. The box should be kept under stable room conditions, away from sources of heat and humidity.

Sources

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