Glass-(Ce)
Chemical formula: Pb₂Ce(CO₃)₃F
A rare mineral from the carbonate, lead, and cerium group, known exclusively from one locality in Canada.
Description
## Characteristics Glassite-(Ce) is an extremely rare mineral from the carbonate group, chemically classified as a lead and cerium fluorocarbonate. It forms very small, thin, tabular crystals that typically combine into rosette-like or spherical aggregates. Individual crystals rarely exceed a fraction of a millimeter. It is colorless, white, or grayish, with a luster described as greasy to pearly. ## Physical Properties The mineral is translucent. Due to its small size and rarity, many of its physical properties, such as hardness or fracture type, have not been thoroughly investigated. Its density, calculated based on chemical composition and crystal structure, is 5.1 g/cm³. ## Colors and Varieties Glassite-(Ce) occurs in a limited color palette: it is colorless, white, or takes on grayish hues. No colored or commercial varieties are known. ## History and Name The mineral was named in honor of Jewell Jeannette Glass (1888-1966), an American petrographer and mineralogist who worked for the United States Geological Survey (USGS). It was described and approved as a new mineral species in 1995. ## Applications Due to its extreme rarity and microscopic size, glassite-(Ce) has no commercial or industrial applications. It is solely an object of scientific interest and a valuable acquisition for specialized collectors of rare minerals.
Diagnostic features
## Identification Amateur identification of glassite-(Ce) is practically impossible. This mineral forms microscopic, tabular crystals in complex parageneses. Definitive identification requires advanced analytical techniques, such as X-ray diffraction (XRD) or X-ray microanalysis (EDS/WDS). A key clue is its occurrence in the specific geological environment of the Poudrette quarry. ## Distinguishing from similar minerals Glassite-(Ce) can be confused with many other rare, white or colorless carbonates and rare earth minerals found in the same locality (e.g., petersenite-(Ce), cordylite-(Ce), ancylite-(Ce)). Visual differentiation without specialized equipment is not possible. ## Crystal Forms Crystals are very thin, with a tabular habit. They most often occur in the form of radial or spherical aggregates and rosettes, composed of densely packed, small lamellae.
Geological environment
## Genesis Glassite-(Ce) forms under very specific geological conditions. It was found in a carbonatite xenolith, which was trapped within a nepheline syenite intrusion. It is a late-stage crystallization mineral in an environment rich in rare earth elements, lead, and fluorine. ## Mineral Associations It co-occurs with a very large number of other, often rare, minerals. The most important include: aegirine, albite, ancylite-(Ce), bastnäsite-(Ce), burbankite, catapleiite, cordylite-(Ce), dawsonite, donnayite-(Y), ewaldite, fluorite, petersenite-(Ce), microcline, natrolite, quartz, rhodochrosite, sérandite, and siderite. ## Localities The only confirmed locality of glassite-(Ce) in the world is the Poudrette quarry on Mont Saint-Hilaire in Quebec, Canada. This is its type locality.
Rarity
Extremely rare
Collector aspects
## Quality Criteria The quality of specimens of this micromineral is assessed based on several criteria. The most important are the abundance of glassite-(Ce) on the rock matrix and the degree of development and sharpness of the crystals forming the aggregates. Specimens where glassite-(Ce) forms well-defined rosettes are highly valued. Additional value comes from its association with other rare and aesthetic minerals from this locality. ## Popular Localities Collector specimens come exclusively from one place in the world - the Poudrette quarry in Mont Saint-Hilaire (Quebec, Canada), which is known for the occurrence of hundreds of unique and rare mineral species.
Care and storage
## Cleaning Specimens of glassite-(Ce) are extremely delicate and usually micro-mounts. Mechanical cleaning is highly risky. For dust removal, it is best to use compressed air from a safe distance. Any contact with water or chemicals should only be undertaken by experts. ## What to Avoid Contact with acids, which rapidly dissolve the mineral (being a carbonate), must be strictly avoided. Ultrasonic cleaners, sudden temperature changes, and exposure to shocks and impacts are not recommended. ## Storage Specimens should be stored in stable, padded micro-mount boxes, protecting them from dust, vibrations, and direct light. Stable humidity and ambient temperature are crucial for preserving the integrity of the delicate crystals.