Peterbaylissite

Chemical formula: Hg<sup>1+</sup><sub>3</sub>CO<sub>3</sub>(OH)·2H<sub>2</sub>O

Peterbaylissite is a very rare, secondary mercury mineral, forming colorless to white, prismatic crystals with a vitreous luster.

## Characteristics Peterbaylissite is a hydrated mercury(I) hydroxycarbonate, occurring as very small, prismatic or tabular crystals, rarely exceeding 0.5 mm in length. It typically forms small aggregates, coatings, or appears as single, scattered crystals. It is colorless to white and transparent, which, combined with the small crystal size, makes it difficult to observe with the naked eye. ## Physical Properties The mineral is characterized by a vitreous luster. Its Mohs hardness is approximately 3, and its density is high, typical for mercury minerals, at 6.16 g/cm³. It is brittle and exhibits perfect cleavage in one direction. ## Colors and Varieties Peterbaylissite is typically colorless or white. No color varieties or commercial varieties have been distinguished. ## History and Name The mineral was discovered at the Clear Creek Claim in San Benito County, California (USA). It was described by Andrew C. Roberts, T. Scott Ercit, J. D. Grice, Robert A. Gault, and Alan J. Criddle in 1996. The name honors Peter Bayliss (b. 1936), an Australian mineralogist and crystallographer from the University of Calgary, in recognition of his contributions to mineralogy, including the systematics of sulfide group minerals. ## Applications Due to its extreme rarity and microscopic size, peterbaylissite has no industrial applications. It is of purely scientific interest and is an object of interest for specialized collectors of rare minerals (so-called micromounts).

Properties

Mohs hardness
3
Luster
Vitreous
Streak
White
Density
6.16
Cleavage
Perfect on {100}
Fracture
Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identifying peterbaylissite under amateur conditions is practically impossible. Identification requires advanced analytical methods such as X-ray diffraction (XRD) and chemical analysis (EDS/WDS). A preliminary indication may be its occurrence in paragenesis with other secondary mercury minerals in known localities. ## Distinguishing from Similar Minerals It can be confused with other colorless or white, secondary mercury minerals, such as eglestonite, terlinguaite, or calomel. Differentiation without specialized equipment is impossible and relies solely on crystallographic and chemical analysis. ## Crystal Forms It forms very small, prismatic or thick tabular crystals, elongated along one axis. They occur as single, isolated crystals or in small, loose aggregates.

Geological environment

## Genesis Peterbaylissite is a secondary mineral, forming in the oxidation zones of mercury deposits. It forms as a result of weathering and alteration of primary mercury minerals, such as cinnabar, in the presence of carbonate-rich waters. ## Mineral Associations This mineral co-occurs with other mercury minerals, especially native mercury, cinnabar, calomel, eglestonite, terlinguaite, and also opal. ## Localities It is an extremely rare mineral, known from only a few locations worldwide. The most important of these are: - Type locality: Clear Creek Claim, New Idria District, San Benito County, California, USA. - Other confirmed occurrences include the Culver-Baer mercury mine in Sonoma County (California, USA) and the El Entredicho mine in Almadenejos (Spain).

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of peterbaylissite specimens is primarily assessed based on the presence of well-formed, sharp, and undamaged crystals, even if they are microscopic in size. Specimens where the crystals are clearly visible, isolated, and contrast with the rock matrix are more highly valued. The abundance of aggregates and association with other rare mercury minerals also increase collecting value. ## Popular Localities The most sought-after specimens come from the type locality at the Clear Creek Claim in California, which is known for providing the world's best specimens of this mineral.

Care and storage

## Cleaning Specimens should only be cleaned very carefully, using compressed air to remove dust. Any contact with water or other liquids is inadvisable due to the mineral's potential solubility and delicacy. ## What to Avoid Absolutely avoid contact with water, acids, and other chemicals. The mineral is sensitive to changes in temperature and humidity. As a mercury mineral, it is toxic – avoid inhaling dust and direct skin contact. Wash hands thoroughly after any contact with the specimen. ## Storage Peterbaylissite specimens, usually in the form of micromounts, should be stored in sealed, stable containers (e.g., micromount boxes) to protect them from mechanical damage, dust, and humidity changes. They should be kept away from heat sources and direct sunlight, in a dry place.

Sources

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