Piilonenite-(Nd)

Chemical formula: NaNd(CO₃)₂·₃H₂O

Extremely rare hydrated sodium neodymium carbonate, known exclusively from the Mont Saint-Hilaire alkaline massif in Canada.

## Characteristics Piilonenite-(Nd) is an extremely rare carbonate mineral that is a hydrated sodium neodymium carbonate. Neodymium, belonging to the lanthanide group (rare earth elements), is the primary metal responsible for the specific nature of this mineral. Piilonenite-(Nd) crystallizes in the orthorhombic system, typically forming microscopic crystals or tiny aggregates that are difficult to discern with the naked eye. ## Physical properties This mineral is characterized by a density of 3.21 g/cm³. It possesses distinct cleavage in one direction, parallel to {010}, and an irregular fracture. The streak of piilonenite-(Nd) is pure white. Due to the microscopic size of the crystals, accurate determination of certain physical properties can be difficult. ## Colors and varieties Piilonenite-(Nd) occurs exclusively in very pale colors - known specimens are colorless or pure white. Because it is a relatively recently described mineral known from only one location worldwide, it has no distinct color varieties or trade names. ## History and name The mineral was discovered in the famous Poudrette quarry, located in the Mont Saint-Hilaire alkaline massif (Quebec Province, Canada). The mineral's name honors Paula C. Piilonen, a Canadian mineralogist at the Canadian Museum of Nature in Ottawa. She was recognized for her significant contributions to the study of alkaline rock mineralogy, particularly her work on the Mont Saint-Hilaire massif. In accordance with the nomenclature rules for rare earth minerals (the Levinson rule), the suffix "-(Nd)" indicates neodymium as the dominant lanthanide in the crystal structure. ## Applications Due to its extreme rarity and the microscopic size of the crystals found, piilonenite-(Nd) has absolutely no industrial or gemological applications. It serves solely as a valuable scientific curiosity for researchers studying the geochemistry of rare earth elements and as an exceptionally rare desirable object for advanced systematic collectors.

Properties

Color: colourless or white
Streak: white
Density: 3.21
Cleavage: {010}
Fracture: Irregular/Uneven
Crystal system: Orthorhombic

Diagnostic features

## Identification Visual identification of piilonenite-(Nd) is practically impossible due to the lack of distinctive macroscopic features and its similarity to many other colorless or white minerals from Mont Saint-Hilaire. Definitive identification requires advanced analytical methods, such as X-ray diffraction (XRD) and micro-area chemical analysis (e.g., EDS/WDS) to confirm the presence of sodium and neodymium. ## Distinction from similar minerals In the field, this mineral can be confused with dozens of other rare carbonates and silicates occurring in the Mont Saint-Hilaire massif (e.g., donnayite-(Y), mckelveyite-(Y)). Distinction relies exclusively on laboratory analysis of chemical composition and crystal structure. ## Crystal habits It crystallizes in the orthorhombic system. It typically forms very fine, microscopic crystals that require observation under magnification.

Geological environment

## Occurrence It forms in specific hydrothermal conditions associated with the evolution of agpaitic igneous rocks. It crystallizes in the late stages of pegmatite and vein formation cutting alkaline intrusions, where strong concentration of rare earth elements occurs. ## Mineral associations It co-occurs with other rare minerals typical of the Mont Saint-Hilaire massif, including numerous carbonates and silicates containing sodium and rare earth elements. ## Localities The only confirmed occurrence in the world (the type locality) is the Poudrette quarry (also known as De-Mix or Uni-Mix) in the Mont Saint-Hilaire massif, Quebec Province, Canada.

Rarity

Extremely rare

For collectors

## Quality criteria The collector value of piilonenite-(Nd) relies exclusively on the extreme rarity of this species and confirmed origin from the type locality. Specimens are micromount in nature, so evaluation focuses mainly on crystal development and state of preservation under a stereomicroscope. ## Market prices Due to the uniqueness of the mineral, specimens rarely appear on the open market. Exchanges and transactions usually take place within a narrow circle of specialists in rare minerals and systematic mineralogy. ## Popular localities All known specimens valued by collectors originate from the Poudrette quarry in Canada.

Care and storage

## Cleaning Specimens should be cleaned exclusively using a very soft brush or a gentle stream of compressed air. Due to the presence of water in the crystal structure and the general solubility of many rare carbonates, washing in water and the use of ultrasonic cleaners must be strictly avoided. ## What to avoid Like any carbonate mineral, piilonenite-(Nd) is highly sensitive to acids, which cause its irreversible decomposition with the release of carbon dioxide. It must be protected from moisture and sudden temperature changes, which could damage the delicate crystals. ## Storage The mineral requires storage in a dry, tightly sealed container. Standard micromount boxes work best, protecting the specimen from dust, atmospheric moisture, and accidental mechanical damage.

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External references

https://www.mindat.org/min-499968.html