Abenakiite-(Ce)

Chemical formula: Na₂₆Ce₃+₆(SiO₃)₆(PO₄)₆(CO₃)₆(S₄+O₂)O

Abenakiite-(Ce) is an extremely rare mineral from the cyclosilicate group, found exclusively at Mont Saint-Hilaire in Canada, distinguished by its very complex chemical composition.

## Characteristics Abenakiite-(Ce) is a very complex sodium and cerium silicate, phosphate, and carbonate. It forms small, tabular crystals with a trigonal outline or occurs as granular and rosette aggregates. It typically ranges from pale to medium brown in color. It is a brittle mineral, and its specimens are almost always microscopic, rarely exceeding a few millimeters. ## Physical Properties The Mohs hardness of abenakiite-(Ce) is 4-5. It has a vitreous luster and is translucent. The mineral's density is approximately 3.21 g/cm³. It exhibits no cleavage, and its fracture is conchoidal. ## Colors and Varieties The only known color of this mineral is brown in various shades, most often pale. No color or commercial varieties are distinguished. ## History and Name The mineral was described in 1994 by George Y. Chao, Joseph A. Mandarino, and Joel D. Grice. Its name honors the Abenaki, the indigenous people inhabiting the area where the discovery was made. The suffix "-(Ce)" indicates that cerium is the dominant rare-earth element in its structure. The type locality is the Poudrette quarry at Mont Saint-Hilaire, Quebec, Canada. ## Uses Due to its extreme rarity and small crystal size, abenakiite-(Ce) has no industrial applications. It is solely an object of scientific interest and a prized acquisition for specialized collectors of rare minerals.

Properties

Mohs hardness: 4-5
Luster: Vitreous
Streak: White
Density: 3.21
Cleavage: None
Fracture: Conchoidal
Transparency: Translucent
Crystal system: Trigonal

Diagnostic features

## Identification Correct identification of abenakiite-(Ce) is extremely difficult and almost always requires advanced analytical methods, such as X-ray diffraction (XRD) or X-ray microanalysis (EDS). Preliminary clues may include its unique locality, brown color, tabular crystal habit, and co-occurrence with other rare alkaline minerals. ## Distinguishing from Similar Minerals Visually, it can be confused with other brown minerals from Mont Saint-Hilaire, such as eudialyte, steacyite, or catapleiite. Differentiation based on external features is practically impossible without specialized equipment. It differs from them in chemical properties and crystal structure. ## Crystal Forms Crystals are usually small, flat, and tabular, with a hexagonal or trigonal outline. They often form aggregates in the shape of rosettes or irregular granular clusters.

Geological environment

## Genesis Abenakiite-(Ce) forms in the late stages of crystallization in pegmatites and sodalite xenoliths, which are found within the nepheline syenite intrusion of the Mont Saint-Hilaire alkaline complex. ## Mineral Associations This mineral co-occurs with a rich assemblage of alkaline minerals. The most common associations include aegirine, nepheline, eudialyte, serandite, steacyite, manganoneptunite, and polylithionite. ## Localities The only confirmed locality of abenakiite-(Ce) in the world is the Poudrette quarry, located on Mont Saint-Hilaire in the Montérégie region, Quebec, Canada.

Rarity

Extremely rare

For collectors

## Quality Criteria For collectors, the most valuable specimens are those with well-formed, sharp crystals, even if they are microscopic. Rich aggregates of the mineral on a rock matrix and aesthetic compositions with other rare minerals from this locality are also highly prized. ## Popular Localities All known and valued specimens of abenakiite-(Ce) by collectors come from a single location – the Poudrette quarry at Mont Saint-Hilaire, Canada. This is the only source of this mineral in the world.

Care and storage

## Cleaning Specimens should only be dry-cleaned, using a soft brush to remove dust. Due to possible reactivity, contact with water, and especially chemical solutions, should be avoided. ## What to Avoid The mineral is soluble in acids. It should be protected from all chemicals, ultrasonic cleaners, high temperatures, and shocks and impacts due to its brittleness. ## Storage It is recommended to store specimens in stable conditions, away from moisture and dust. The safest way is to place the mineral in a sealed "micromount" box, which protects it from mechanical damage and loss.

External references

https://en.wikipedia.org/wiki/https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FAbenakiite-(Ce)