Alicewilsonite-(YLa)

Chemical formula: Na₂Sr₂YLa(CO₃)₆·₃H₂O

A very rare, hydrated sodium, strontium, yttrium, and lanthanum carbonate, forming small, tabular crystals in a unique geological environment.

## Characteristics Alicewilsonite-(YLa) is a complex, hydrated mineral from the carbonate group. It occurs as small, well-formed crystals with a tabular or short-prismatic habit, often aggregated into rosettes or radiating clusters. Specimens are typically very small, classifying it as a typical micromount mineral. Its brittle crystals rarely exceed a few millimeters in length. ## Physical Properties This mineral is characterized by low hardness, approximately 3 on the Mohs scale, making it susceptible to scratching. It has a vitreous luster, and on cleavage surfaces, it may exhibit a pearly luster. It is transparent to translucent. The calculated density for this mineral is approximately 3.35 g/cm³. ## Colors and Varieties Alicewilsonite-(YLa) is most often colorless, white, or takes on pale shades of pink and yellow. It has no named commercial varieties. There is an analog with dominant cerium, named alicewilsonite-(YCe), which forms a series with it. The mineral name with the suffix -(YLa) indicates the dominance of yttrium (Y) and lanthanum (La) in specific positions within its crystal structure. ## History and Name The mineral is named in honor of Alice Evelyn Wilson (1881–1964), a pioneering Canadian geologist and paleontologist, the first woman to become a member of the Royal Society of Canada. The mineral was officially recognized by the International Mineralogical Association (IMA) in 2020. Its discovery took place at the Poudrette quarry on Mont Saint-Hilaire in Quebec, Canada, which is its type locality. ## Applications Due to its extreme rarity and small crystal size, alicewilsonite-(YLa) has no industrial applications. It is solely an object of scientific interest and a prized acquisition in advanced systematic and micromount mineral collections.

Properties

Mohs hardness: 3
Luster: Vitreous to Pearly
Streak: White
Density: 3.35
Cleavage: Good on {010}
Fracture: Uneven
Transparency: Transparent to Translucent
Crystal system: Triclinic

Diagnostic features

## Identification Identification of alicewilsonite-(YLa) is extremely difficult without advanced analytical methods, such as X-ray diffraction (XRD) or X-ray microanalysis (EDS/WDS). In collector conditions, key clues include: characteristic locality (Mont Saint-Hilaire), crystal habit (small, tabular, often in rosettes), low hardness, and co-occurrence with other rare alkaline minerals. ## Distinguishing from Similar Minerals It can be confused with other rare carbonates from Mont Saint-Hilaire, such as its analog alicewilsonite-(YCe) or minerals from the ancylite and mckelveyite groups. Definitive differentiation is possible only based on chemical composition analysis. From more common carbonates, like calcite, it is distinguished by its specific crystal habit and occurrence environment. ## Crystal Forms Crystals are most often tabular or thick-tabular, hexagonal in outline. They often form radiating or rosette-like aggregates, where individual crystals overlap.

Geological environment

## Genesis Alicewilsonite-(YLa) is a hydrothermal mineral. It forms in the late stages of crystallization in cavities and fissures within nepheline syenites and associated pegmatites. This environment, rich in rare earth elements, strontium, and sodium, favors the formation of unique and complex minerals. ## Mineral Associations This mineral occurs in association with many other rare species characteristic of Mont Saint-Hilaire. The most common associated minerals include aegirine, albite, microcline, analcime, sericite, as well as rarer ones such as ancylite-(Ce), mckelveyite-(Y), and its analog alicewilsonite-(YCe). ## Localities The only confirmed locality of alicewilsonite-(YLa) in the world is its type locality – the famous Poudrette quarry, located on Mont Saint-Hilaire, in the Montérégie region, Quebec, Canada.

Rarity

Extremely rare

For collectors

## Quality Criteria For a micromount mineral like alicewilsonite-(YLa), specimens with sharp, well-formed, and undamaged crystals are most highly valued. The value of a specimen increases with the size and transparency of the crystals, their aesthetic arrangement on the rock matrix, and the intensity of any coloration (e.g., pink). The presence of rare associated minerals also enhances its appeal. ## Popular Localities The most prized, and indeed the only available specimens on the market, come from the Poudrette quarry on Mont Saint-Hilaire in Canada. This locality is a mecca for collectors of rare minerals, and specimens from it have particular value.

Care and storage

## Cleaning The mineral is very soft and delicate. For dust removal, it is best to use a soft brush or a photographic air blower. Wet cleaning should be avoided. If absolutely necessary, a minimal amount of distilled water can be used, applied precisely, and the specimen immediately dried. ## What to Avoid As a carbonate, alicewilsonite-(YLa) is sensitive to acids, which cause its rapid decomposition. Ultrasonic cleaners, chemical agents, and sudden temperature changes should be avoided. Due to its low hardness, it is susceptible to mechanical damage and scratching. ## Storage Specimens should be stored in separate, stable "micromount" boxes, away from harder minerals. Protection from dust, vibrations, and direct sunlight is recommended, as sunlight could theoretically affect the pale coloration of some crystals.

Sources

IMA Mineral List (CNMNC)